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authorCharles Harris <charlesr.harris@gmail.com>2010-08-17 01:52:11 +0000
committerCharles Harris <charlesr.harris@gmail.com>2010-08-17 01:52:11 +0000
commit8f1b2d6442f1d96886e3f83886f57b0dca9106e3 (patch)
tree2a488b03e9656c3eced5e513e1808314b07902da /numpy
parent00b74ad6aa0931985580afcca692c89c411069ca (diff)
downloadnumpy-8f1b2d6442f1d96886e3f83886f57b0dca9106e3.tar.gz
ENH: Add support for Legendre polynomials.
Diffstat (limited to 'numpy')
-rw-r--r--numpy/polynomial/__init__.py1
-rw-r--r--numpy/polynomial/chebyshev.py5
-rw-r--r--numpy/polynomial/legendre.py1249
-rw-r--r--numpy/polynomial/tests/test_chebyshev.py4
-rw-r--r--numpy/polynomial/tests/test_legendre.py533
5 files changed, 1788 insertions, 4 deletions
diff --git a/numpy/polynomial/__init__.py b/numpy/polynomial/__init__.py
index 7e755ca52..6b004acc4 100644
--- a/numpy/polynomial/__init__.py
+++ b/numpy/polynomial/__init__.py
@@ -15,6 +15,7 @@ information can be found in the docstring for the module of interest.
"""
from polynomial import *
from chebyshev import *
+from legendre import *
from polyutils import *
from numpy.testing import Tester
diff --git a/numpy/polynomial/chebyshev.py b/numpy/polynomial/chebyshev.py
index 23f8a728f..ea064a695 100644
--- a/numpy/polynomial/chebyshev.py
+++ b/numpy/polynomial/chebyshev.py
@@ -408,9 +408,10 @@ def cheb2poly(cs) :
else:
c0 = cs[-2]
c1 = cs[-1]
- for i in range(n - 3, -1, -1) :
+ # i is the current degree of c1
+ for i in range(n - 1, 1, -1) :
tmp = c0
- c0 = polysub(cs[i], c1)
+ c0 = polysub(cs[i - 2], c1)
c1 = polyadd(tmp, polymulx(c1)*2)
return polyadd(c0, polymulx(c1))
diff --git a/numpy/polynomial/legendre.py b/numpy/polynomial/legendre.py
new file mode 100644
index 000000000..acd2d0554
--- /dev/null
+++ b/numpy/polynomial/legendre.py
@@ -0,0 +1,1249 @@
+"""
+Objects for dealing with Legendre series.
+
+This module provides a number of objects (mostly functions) useful for
+dealing with Legendre series, including a `Legendre` class that
+encapsulates the usual arithmetic operations. (General information
+on how this module represents and works with such polynomials is in the
+docstring for its "parent" sub-package, `numpy.polynomial`).
+
+Constants
+---------
+- `legdomain` -- Legendre series default domain, [-1,1].
+- `legzero` -- Legendre series that evaluates identically to 0.
+- `legone` -- Legendre series that evaluates identically to 1.
+- `legx` -- Legendre series for the identity map, ``f(x) = x``.
+
+Arithmetic
+----------
+- `legmulx` -- multiply a Legendre series in ``P_i(x)`` by ``x``.
+- `legadd` -- add two Legendre series.
+- `legsub` -- subtract one Legendre series from another.
+- `legmul` -- multiply two Legendre series.
+- `legdiv` -- divide one Legendre series by another.
+- `legval` -- evaluate a Legendre series at given points.
+
+Calculus
+--------
+- `legder` -- differentiate a Legendre series.
+- `legint` -- integrate a Legendre series.
+
+Misc Functions
+--------------
+- `legfromroots` -- create a Legendre series with specified roots.
+- `legroots` -- find the roots of a Legendre series.
+- `legvander` -- Vandermonde-like matrix for Legendre polynomials.
+- `legfit` -- least-squares fit returning a Legendre series.
+- `legtrim` -- trim leading coefficients from a Legendre series.
+- `legline` -- Legendre series of given straight line.
+- `leg2poly` -- convert a Legendre series to a polynomial.
+- `poly2leg` -- convert a polynomial to a Legendre series.
+
+Classes
+-------
+- `Legendre` -- A Legendre series class.
+
+See also
+--------
+`numpy.polynomial`
+
+Notes
+-----
+The implementations of multiplication, division, integration, and
+differentiation use the algebraic identities [1]_:
+
+.. math ::
+ T_n(x) = \\frac{z^n + z^{-n}}{2} \\\\
+ z\\frac{dx}{dz} = \\frac{z - z^{-1}}{2}.
+
+where
+
+.. math :: x = \\frac{z + z^{-1}}{2}.
+
+These identities allow a Chebyshev series to be expressed as a finite,
+symmetric Laurent series. In this module, this sort of Laurent series
+is referred to as a "z-series."
+
+References
+----------
+.. [1] A. T. Benjamin, et al., "Combinatorial Trigonometry with Chebyshev
+ Polynomials," *Journal of Statistical Planning and Inference 14*, 2008
+ (preprint: http://www.math.hmc.edu/~benjamin/papers/CombTrig.pdf, pg. 4)
+
+"""
+from __future__ import division
+
+__all__ = ['legzero', 'legone', 'legx', 'legdomain', 'legline',
+ 'legadd', 'legsub', 'legmulx', 'legmul', 'legdiv', 'legval',
+ 'legder', 'legint', 'leg2poly', 'poly2leg', 'legfromroots',
+ 'legvander', 'legfit', 'legtrim', 'legroots', 'Legendre']
+
+import numpy as np
+import numpy.linalg as la
+import polyutils as pu
+import warnings
+from polytemplate import polytemplate
+
+legtrim = pu.trimcoef
+
+def poly2leg(pol) :
+ """
+ poly2leg(pol)
+
+ Convert a polynomial to a Legendre series.
+
+ Convert an array representing the coefficients of a polynomial (relative
+ to the "standard" basis) ordered from lowest degree to highest, to an
+ array of the coefficients of the equivalent Legendre series, ordered
+ from lowest to highest degree.
+
+ Parameters
+ ----------
+ pol : array_like
+ 1-d array containing the polynomial coefficients
+
+ Returns
+ -------
+ cs : ndarray
+ 1-d array containing the coefficients of the equivalent Legendre
+ series.
+
+ See Also
+ --------
+ leg2poly
+
+ Notes
+ -----
+ The easy way to do conversions between polynomial basis sets
+ is to use the convert method of a class instance.
+
+ Examples
+ --------
+ >>> from numpy import polynomial as P
+ >>> p = P.Polynomial(np.arange(4))
+ >>> p
+ Polynomial([ 0., 1., 2., 3.], [-1., 1.])
+ >>> c = P.Legendre(P.poly2leg(p.coef))
+ >>> c
+ Legendre([ 1. , 3.25, 1. , 0.75], [-1., 1.])
+
+ """
+ [pol] = pu.as_series([pol])
+ deg = len(pol) - 1
+ res = 0
+ for i in range(deg, -1, -1) :
+ res = legadd(legmulx(res), pol[i])
+ return res
+
+
+def leg2poly(cs) :
+ """
+ Convert a Legendre series to a polynomial.
+
+ Convert an array representing the coefficients of a Legendre series,
+ ordered from lowest degree to highest, to an array of the coefficients
+ of the equivalent polynomial (relative to the "standard" basis) ordered
+ from lowest to highest degree.
+
+ Parameters
+ ----------
+ cs : array_like
+ 1-d array containing the Legendre series coefficients, ordered
+ from lowest order term to highest.
+
+ Returns
+ -------
+ pol : ndarray
+ 1-d array containing the coefficients of the equivalent polynomial
+ (relative to the "standard" basis) ordered from lowest order term
+ to highest.
+
+ See Also
+ --------
+ poly2leg
+
+ Notes
+ -----
+ The easy way to do conversions between polynomial basis sets
+ is to use the convert method of a class instance.
+
+ Examples
+ --------
+ >>> from numpy import polynomial as P
+ >>> c = P.Chebyshev(np.arange(4))
+ >>> c
+ Chebyshev([ 0., 1., 2., 3.], [-1., 1.])
+ >>> p = P.Polynomial(P.cheb2poly(c.coef))
+ >>> p
+ Polynomial([ -2., -8., 4., 12.], [-1., 1.])
+
+ """
+ from polynomial import polyadd, polysub, polymulx
+
+ [cs] = pu.as_series([cs])
+ n = len(cs)
+ if n < 3:
+ return cs
+ else:
+ c0 = cs[-2]
+ c1 = cs[-1]
+ # i is the current degree of c1
+ for i in range(n - 1, 1, -1) :
+ tmp = c0
+ c0 = polysub(cs[i - 2], (c1*(i - 1))/i)
+ c1 = polyadd(tmp, (polymulx(c1)*(2*i - 1))/i)
+ return polyadd(c0, polymulx(c1))
+
+#
+# These are constant arrays are of integer type so as to be compatible
+# with the widest range of other types, such as Decimal.
+#
+
+# Legendre
+legdomain = np.array([-1,1])
+
+# Legendre coefficients representing zero.
+legzero = np.array([0])
+
+# Legendre coefficients representing one.
+legone = np.array([1])
+
+# Legendre coefficients representing the identity x.
+legx = np.array([0,1])
+
+
+def legline(off, scl) :
+ """
+ Legendre series whose graph is a straight line.
+
+
+
+ Parameters
+ ----------
+ off, scl : scalars
+ The specified line is given by ``off + scl*x``.
+
+ Returns
+ -------
+ y : ndarray
+ This module's representation of the Legendre series for
+ ``off + scl*x``.
+
+ See Also
+ --------
+ polyline, chebline
+
+ Examples
+ --------
+ >>> import numpy.polynomial.legendre as L
+ >>> L.legline(3,2)
+ array([3, 2])
+ >>> L.legval(-3, L.chebline(3,2)) # should be -3
+ -3.0
+
+ """
+ if scl != 0 :
+ return np.array([off,scl])
+ else :
+ return np.array([off])
+
+
+def legtimesx(cs):
+ """Multiply a Legendre series by x.
+
+ Multiply the Legendre series `cs` by x, where x is the independent
+ variable.
+
+
+ Parameters
+ ----------
+ cs : array_like
+ 1-d array of Legendre series coefficients ordered from low to
+ high.
+
+ Returns
+ -------
+ out : ndarray
+ Array representing the result of the multiplication.
+
+ Notes
+ -----
+ The multiplication uses the recursion relationship for Legendre
+ polynomials in the form
+
+ .. math::
+
+ xP_i(x) = ((i + 1)*P_{i + 1}(x) + i*P_{i - 1}(x))/(2i + 1)
+
+ """
+ # cs is a trimmed copy
+ [cs] = pu.as_series([cs])
+ # The zero series needs special treatment
+ if len(cs) == 1 and cs[0] == 0:
+ return cs
+
+ prd = np.empty(len(cs) + 1, dtype=cs.dtype)
+ prd[0] = cs[0]*0
+ prd[1] = cs[0]
+ for i in range(1, len(cs)):
+ j = i + 1
+ k = i - 1
+ s = i + j
+ prd[j] = (cs[i]*j)/s
+ prd[k] += (cs[i]*i)/s
+ return prd
+
+
+def chebline(off, scl) :
+ """
+ Chebyshev series whose graph is a straight line.
+
+
+
+ Parameters
+ ----------
+ off, scl : scalars
+ The specified line is given by ``off + scl*x``.
+
+ Returns
+ -------
+ y : ndarray
+ This module's representation of the Chebyshev series for
+ ``off + scl*x``.
+
+ See Also
+ --------
+ polyline
+
+ Examples
+ --------
+ >>> import numpy.polynomial.chebyshev as C
+ >>> C.chebline(3,2)
+ array([3, 2])
+ >>> C.chebval(-3, C.chebline(3,2)) # should be -3
+ -3.0
+
+ """
+ if scl != 0 :
+ return np.array([off,scl])
+ else :
+ return np.array([off])
+
+
+def legfromroots(roots) :
+ """
+ Generate a Legendre series with the given roots.
+
+ Return the array of coefficients for the P-series whose roots (a.k.a.
+ "zeros") are given by *roots*. The returned array of coefficients is
+ ordered from lowest order "term" to highest, and zeros of multiplicity
+ greater than one must be included in *roots* a number of times equal
+ to their multiplicity (e.g., if `2` is a root of multiplicity three,
+ then [2,2,2] must be in *roots*).
+
+ Parameters
+ ----------
+ roots : array_like
+ Sequence containing the roots.
+
+ Returns
+ -------
+ out : ndarray
+ 1-d array of the Legendre series coefficients, ordered from low to
+ high. If all roots are real, ``out.dtype`` is a float type;
+ otherwise, ``out.dtype`` is a complex type, even if all the
+ coefficients in the result are real (see Examples below).
+
+ See Also
+ --------
+ polyfromroots, chebfromroots
+
+ Notes
+ -----
+ What is returned are the :math:`c_i` such that:
+
+ .. math::
+
+ \\sum_{i=0}^{n} c_i*P_i(x) = \\prod_{i=0}^{n} (x - roots[i])
+
+ where ``n == len(roots)`` and :math:`P_i(x)` is the `i`-th Legendre
+ (basis) polynomial over the domain `[-1,1]`. Note that, unlike
+ `polyfromroots`, due to the nature of the Legendre basis set, the
+ above identity *does not* imply :math:`c_n = 1` identically (see
+ Examples).
+
+ Examples
+ --------
+ >>> import numpy.polynomial.legendre as L
+ >>> L.legfromroots((-1,0,1)) # x^3 - x relative to the standard basis
+ array([ 0. , -0.4, 0. , 0.4])
+ >>> j = complex(0,1)
+ >>> L.legfromroots((-j,j)) # x^2 + 1 relative to the standard basis
+ array([ 1.33333333+0.j, 0.00000000+0.j, 0.66666667+0.j])
+
+ """
+ if len(roots) == 0 :
+ return np.ones(1)
+ else :
+ [roots] = pu.as_series([roots], trim=False)
+ prd = np.array([1], dtype=roots.dtype)
+ for r in roots:
+ prd = legsub(legmulx(prd), r*prd)
+ return prd
+
+
+def legadd(c1, c2):
+ """
+ Add one Legendre series to another.
+
+ Returns the sum of two Legendre series `c1` + `c2`. The arguments
+ are sequences of coefficients ordered from lowest order term to
+ highest, i.e., [1,2,3] represents the series ``P_0 + 2*P_1 + 3*P_2``.
+
+ Parameters
+ ----------
+ c1, c2 : array_like
+ 1-d arrays of Legendre series coefficients ordered from low to
+ high.
+
+ Returns
+ -------
+ out : ndarray
+ Array representing the Legendre series of their sum.
+
+ See Also
+ --------
+ legsub, legmul, legdiv, legpow
+
+ Notes
+ -----
+ Unlike multiplication, division, etc., the sum of two Legendre series
+ is a Legendre series (without having to "reproject" the result onto
+ the basis set) so addition, just like that of "standard" polynomials,
+ is simply "component-wise."
+
+ Examples
+ --------
+ >>> from numpy.polynomial import legendre as L
+ >>> c1 = (1,2,3)
+ >>> c2 = (3,2,1)
+ >>> L.legadd(c1,c2)
+ array([ 4., 4., 4.])
+
+ """
+ # c1, c2 are trimmed copies
+ [c1, c2] = pu.as_series([c1, c2])
+ if len(c1) > len(c2) :
+ c1[:c2.size] += c2
+ ret = c1
+ else :
+ c2[:c1.size] += c1
+ ret = c2
+ return pu.trimseq(ret)
+
+
+def legsub(c1, c2):
+ """
+ Subtract one Legendre series from another.
+
+ Returns the difference of two Legendre series `c1` - `c2`. The
+ sequences of coefficients are from lowest order term to highest, i.e.,
+ [1,2,3] represents the series ``P_0 + 2*P_1 + 3*P_2``.
+
+ Parameters
+ ----------
+ c1, c2 : array_like
+ 1-d arrays of Legendre series coefficients ordered from low to
+ high.
+
+ Returns
+ -------
+ out : ndarray
+ Of Legendre series coefficients representing their difference.
+
+ See Also
+ --------
+ legadd, legmul, legdiv, legpow
+
+ Notes
+ -----
+ Unlike multiplication, division, etc., the difference of two Legendre
+ series is a Legendre series (without having to "reproject" the result
+ onto the basis set) so subtraction, just like that of "standard"
+ polynomials, is simply "component-wise."
+
+ Examples
+ --------
+ >>> from numpy.polynomial import legendre as L
+ >>> c1 = (1,2,3)
+ >>> c2 = (3,2,1)
+ >>> L.legsub(c1,c2)
+ array([-2., 0., 2.])
+ >>> L.legsub(c2,c1) # -C.legsub(c1,c2)
+ array([ 2., 0., -2.])
+
+ """
+ # c1, c2 are trimmed copies
+ [c1, c2] = pu.as_series([c1, c2])
+ if len(c1) > len(c2) :
+ c1[:c2.size] -= c2
+ ret = c1
+ else :
+ c2 = -c2
+ c2[:c1.size] += c1
+ ret = c2
+ return pu.trimseq(ret)
+
+
+def legmulx(cs):
+ """Multiply a Legendre series by x.
+
+ Multiply the Legendre series `cs` by x, where x is the independent
+ variable.
+
+
+ Parameters
+ ----------
+ cs : array_like
+ 1-d array of Legendre series coefficients ordered from low to
+ high.
+
+ Returns
+ -------
+ out : ndarray
+ Array representing the result of the multiplication.
+
+ Notes
+ -----
+ The multiplication uses the recursion relationship for Legendre
+ polynomials in the form
+
+ .. math::
+
+ xP_i(x) = ((i + 1)*P_{i + 1}(x) + i*P_{i - 1}(x))/(2i + 1)
+
+ """
+ # cs is a trimmed copy
+ [cs] = pu.as_series([cs])
+ # The zero series needs special treatment
+ if len(cs) == 1 and cs[0] == 0:
+ return cs
+
+ prd = np.empty(len(cs) + 1, dtype=cs.dtype)
+ prd[0] = cs[0]*0
+ prd[1] = cs[0]
+ for i in range(1, len(cs)):
+ j = i + 1
+ k = i - 1
+ s = i + j
+ prd[j] = (cs[i]*j)/s
+ prd[k] += (cs[i]*i)/s
+ return prd
+
+
+def legmul(c1, c2):
+ """
+ Multiply one Legendre series by another.
+
+ Returns the product of two Legendre series `c1` * `c2`. The arguments
+ are sequences of coefficients, from lowest order "term" to highest,
+ e.g., [1,2,3] represents the series ``P_0 + 2*P_1 + 3*P_2``.
+
+ Parameters
+ ----------
+ c1, c2 : array_like
+ 1-d arrays of Legendre series coefficients ordered from low to
+ high.
+
+ Returns
+ -------
+ out : ndarray
+ Of Legendre series coefficients representing their product.
+
+ See Also
+ --------
+ legadd, legsub, legdiv, legpow
+
+ Notes
+ -----
+ In general, the (polynomial) product of two C-series results in terms
+ that are not in the Chebyshev polynomial basis set. Thus, to express
+ the product as a C-series, it is typically necessary to "re-project"
+ the product onto said basis set, which typically produces
+ "un-intuitive" (but correct) results; see Examples section below.
+
+ Examples
+ --------
+ >>> from numpy.polynomial import legendre as P
+ >>> c1 = (1,2,3)
+ >>> c2 = (3,2)
+ >>> P.legmul(c1,c2) # multiplication requires "reprojection"
+ array([ 4.33333333, 10.4 , 11.66666667, 3.6 ])
+
+ """
+ # s1, s2 are trimmed copies
+ [c1, c2] = pu.as_series([c1, c2])
+
+ if len(c1) > len(c2):
+ cs = c2
+ xs = c1
+ else:
+ cs = c1
+ xs = c2
+
+ if len(cs) == 1:
+ c0 = cs[0]*xs
+ c1 = 0
+ elif len(cs) == 2:
+ c0 = cs[0]*xs
+ c1 = cs[1]*xs
+ else :
+ nd = len(cs)
+ c0 = cs[-2]*xs
+ c1 = cs[-1]*xs
+ for i in range(3, len(cs) + 1) :
+ tmp = c0
+ nd = nd - 1
+ c0 = legsub(cs[-i]*xs, (c1*(nd - 1))/nd)
+ c1 = legadd(tmp, (legmulx(c1)*(2*nd - 1))/nd)
+ return legadd(c0, legmulx(c1))
+
+
+def legdiv(c1, c2):
+ """
+ Divide one Legendre series by another.
+
+ Returns the quotient-with-remainder of two Legendre series
+ `c1` / `c2`. The arguments are sequences of coefficients from lowest
+ order "term" to highest, e.g., [1,2,3] represents the series
+ ``P_0 + 2*P_1 + 3*P_2``.
+
+ Parameters
+ ----------
+ c1, c2 : array_like
+ 1-d arrays of Legendre series coefficients ordered from low to
+ high.
+
+ Returns
+ -------
+ [quo, rem] : ndarrays
+ Of Legendre series coefficients representing the quotient and
+ remainder.
+
+ See Also
+ --------
+ legadd, legsub, legmul, legpow
+
+ Notes
+ -----
+ In general, the (polynomial) division of one Legendre series by another
+ results in quotient and remainder terms that are not in the Legendre
+ polynomial basis set. Thus, to express these results as a Legendre
+ series, it is necessary to "re-project" the results onto the Legendre
+ basis set, which may produce "un-intuitive" (but correct) results; see
+ Examples section below.
+
+ Examples
+ --------
+ >>> from numpy.polynomial import legendre as L
+ >>> c1 = (1,2,3)
+ >>> c2 = (3,2,1)
+ >>> L.legdiv(c1,c2) # quotient "intuitive," remainder not
+ (array([ 3.]), array([-8., -4.]))
+ >>> c2 = (0,1,2,3)
+ >>> L.legdiv(c2,c1) # neither "intuitive"
+ (array([-0.07407407, 1.66666667]), array([-1.03703704, -2.51851852]))
+
+ """
+ # c1, c2 are trimmed copies
+ [c1, c2] = pu.as_series([c1, c2])
+ if c2[-1] == 0 :
+ raise ZeroDivisionError()
+
+ lc1 = len(c1)
+ lc2 = len(c2)
+ if lc1 < lc2 :
+ return c1[:1]*0, c1
+ elif lc2 == 1 :
+ return c1/c2[-1], c1[:1]*0
+ else :
+ quo = np.empty(lc1 - lc2 + 1, dtype=c1.dtype)
+ rem = c1
+ for i in range(lc1 - lc2, - 1, -1):
+ p = legmul([0]*i + [1], c2)
+ q = rem[-1]/p[-1]
+ rem = rem[:-1] - q*p[:-1]
+ quo[i] = q
+ return quo, pu.trimseq(rem)
+
+
+def legpow(cs, pow, maxpower=16) :
+ """Raise a Legendre series to a power.
+
+ Returns the Legendre series `cs` raised to the power `pow`. The
+ arguement `cs` is a sequence of coefficients ordered from low to high.
+ i.e., [1,2,3] is the series ``P_0 + 2*P_1 + 3*P_2.``
+
+ Parameters
+ ----------
+ cs : array_like
+ 1d array of Legendre series coefficients ordered from low to
+ high.
+ pow : integer
+ Power to which the series will be raised
+ maxpower : integer, optional
+ Maximum power allowed. This is mainly to limit growth of the series
+ to umanageable size. Default is 16
+
+ Returns
+ -------
+ coef : ndarray
+ Legendre series of power.
+
+ See Also
+ --------
+ legadd, legsub, legmul, legdiv
+
+ Examples
+ --------
+
+ """
+ # cs is a trimmed copy
+ [cs] = pu.as_series([cs])
+ power = int(pow)
+ if power != pow or power < 0 :
+ raise ValueError("Power must be a non-negative integer.")
+ elif maxpower is not None and power > maxpower :
+ raise ValueError("Power is too large")
+ elif power == 0 :
+ return np.array([1], dtype=cs.dtype)
+ elif power == 1 :
+ return cs
+ else :
+ # This can be made more efficient by using powers of two
+ # in the usual way.
+ prd = cs
+ for i in range(2, power + 1) :
+ prd = legmul(prd, cs)
+ return prd
+
+
+def legder(cs, m=1, scl=1) :
+ """
+ Differentiate a Legendre series.
+
+ Returns the series `cs` differentiated `m` times. At each iteration the
+ result is multiplied by `scl` (the scaling factor is for use in a linear
+ change of variable). The argument `cs` is the sequence of coefficients
+ from lowest order "term" to highest, e.g., [1,2,3] represents the series
+ ``P_0 + 2*P_1 + 3*P_2``.
+
+ Parameters
+ ----------
+ cs: array_like
+ 1-d array of Legendre series coefficients ordered from low to high.
+ m : int, optional
+ Number of derivatives taken, must be non-negative. (Default: 1)
+ scl : scalar, optional
+ Each differentiation is multiplied by `scl`. The end result is
+ multiplication by ``scl**m``. This is for use in a linear change of
+ variable. (Default: 1)
+
+ Returns
+ -------
+ der : ndarray
+ Legendre series of the derivative.
+
+ See Also
+ --------
+ legint
+
+ Notes
+ -----
+ In general, the result of differentiating a Legendre series does not
+ resemble the same operation on a power series. Thus the result of this
+ function may be "un-intuitive," albeit correct; see Examples section
+ below.
+
+ Examples
+ --------
+ >>> from numpy.polynomial import legendre as L
+ >>> cs = (1,2,3,4)
+ >>> L.legder(cs)
+ array([ 6., 9., 20.])
+ >>> L.legder(cs,3)
+ array([ 60.])
+ >>> L.legder(cs,scl=-1)
+ array([ -6., -9., -20.])
+ >>> L.legder(cs,2,-1)
+ array([ 9., 60.])
+
+ """
+ cnt = int(m)
+
+ if cnt != m:
+ raise ValueError, "The order of derivation must be integer"
+ if cnt < 0 :
+ raise ValueError, "The order of derivation must be non-negative"
+
+ # cs is a trimmed copy
+ [cs] = pu.as_series([cs])
+ if cnt == 0:
+ return cs
+ elif cnt >= len(cs):
+ return cs[:1]*0
+ else :
+ for i in range(cnt):
+ n = len(cs) - 1
+ cs *= scl
+ der = np.empty(n, dtype=cs.dtype)
+ for j in range(n, 0, -1):
+ der[j - 1] = (2*j - 1)*cs[j]
+ cs[j - 2] += cs[j]
+ cs = der
+ return cs
+
+
+def legint(cs, m=1, k=[], lbnd=0, scl=1):
+ """
+ Integrate a Legendre series.
+
+ Returns a Legendre series that is the Legendre series `cs`, integrated
+ `m` times from `lbnd` to `x`. At each iteration the resulting series
+ is **multiplied** by `scl` and an integration constant, `k`, is added.
+ The scaling factor is for use in a linear change of variable. ("Buyer
+ beware": note that, depending on what one is doing, one may want `scl`
+ to be the reciprocal of what one might expect; for more information,
+ see the Notes section below.) The argument `cs` is a sequence of
+ coefficients, from lowest order Legendre series "term" to highest,
+ e.g., [1,2,3] represents the series :math:`P_0(x) + 2P_1(x) + 3P_2(x)`.
+
+ Parameters
+ ----------
+ cs : array_like
+ 1-d array of Legendre series coefficients, ordered from low to high.
+ m : int, optional
+ Order of integration, must be positive. (Default: 1)
+ k : {[], list, scalar}, optional
+ Integration constant(s). The value of the first integral at
+ ``lbnd`` is the first value in the list, the value of the second
+ integral at ``lbnd`` is the second value, etc. If ``k == []`` (the
+ default), all constants are set to zero. If ``m == 1``, a single
+ scalar can be given instead of a list.
+ lbnd : scalar, optional
+ The lower bound of the integral. (Default: 0)
+ scl : scalar, optional
+ Following each integration the result is *multiplied* by `scl`
+ before the integration constant is added. (Default: 1)
+
+ Returns
+ -------
+ S : ndarray
+ Legendre series coefficients of the integral.
+
+ Raises
+ ------
+ ValueError
+ If ``m < 0``, ``len(k) > m``, ``np.isscalar(lbnd) == False``, or
+ ``np.isscalar(scl) == False``.
+
+ See Also
+ --------
+ legder
+
+ Notes
+ -----
+ Note that the result of each integration is *multiplied* by `scl`.
+ Why is this important to note? Say one is making a linear change of
+ variable :math:`u = ax + b` in an integral relative to `x`. Then
+ :math:`dx = du/a`, so one will need to set `scl` equal to :math:`1/a`
+ - perhaps not what one would have first thought.
+
+ Also note that, in general, the result of integrating a C-series needs
+ to be "re-projected" onto the C-series basis set. Thus, typically,
+ the result of this function is "un-intuitive," albeit correct; see
+ Examples section below.
+
+ Examples
+ --------
+ >>> from numpy.polynomial import legyshev as L
+ >>> cs = (1,2,3)
+ >>> L.legint(cs)
+ array([ 0.5, -0.5, 0.5, 0.5])
+ >>> L.legint(cs,3)
+ array([ 0.03125 , -0.1875 , 0.04166667, -0.05208333, 0.01041667,
+ 0.00625 ])
+ >>> L.legint(cs, k=3)
+ array([ 3.5, -0.5, 0.5, 0.5])
+ >>> L.legint(cs,lbnd=-2)
+ array([ 8.5, -0.5, 0.5, 0.5])
+ >>> L.legint(cs,scl=-2)
+ array([-1., 1., -1., -1.])
+
+ """
+ cnt = int(m)
+ if np.isscalar(k) :
+ k = [k]
+
+ if cnt != m:
+ raise ValueError, "The order of integration must be integer"
+ if cnt < 0 :
+ raise ValueError, "The order of integration must be non-negative"
+ if len(k) > cnt :
+ raise ValueError, "Too many integration constants"
+
+ # cs is a trimmed copy
+ [cs] = pu.as_series([cs])
+ if cnt == 0:
+ return cs
+
+ k = list(k) + [0]*(cnt - len(k))
+ for i in range(cnt) :
+ n = len(cs)
+ cs *= scl
+ if n == 1 and cs[0] == 0:
+ cs[0] += k[i]
+ else:
+ tmp = np.empty(n + 1, dtype=cs.dtype)
+ tmp[0] = cs[0]*0
+ tmp[1] = cs[0]
+ for j in range(1, n):
+ t = cs[j]/(2*j + 1)
+ tmp[j + 1] = t
+ tmp[j - 1] -= t
+ tmp[0] += k[i] - legval(lbnd, tmp)
+ cs = tmp
+ return cs
+
+
+def legval(x, cs):
+ """Evaluate a Legendre series.
+
+ If `cs` is of length `n`, this function returns :
+
+ ``p(x) = cs[0]*P_0(x) + cs[1]*P_1(x) + ... + cs[n-1]*P_{n-1}(x)``
+
+ If x is a sequence or array then p(x) will have the same shape as x.
+ If r is a ring_like object that supports multiplication and addition
+ by the values in `cs`, then an object of the same type is returned.
+
+ Parameters
+ ----------
+ x : array_like, ring_like
+ Array of numbers or objects that support multiplication and
+ addition with themselves and with the elements of `cs`.
+ cs : array_like
+ 1-d array of Chebyshev coefficients ordered from low to high.
+
+ Returns
+ -------
+ values : ndarray, ring_like
+ If the return is an ndarray then it has the same shape as `x`.
+
+ See Also
+ --------
+ legfit
+
+ Examples
+ --------
+
+ Notes
+ -----
+ The evaluation uses Clenshaw recursion, aka synthetic division.
+
+ Examples
+ --------
+
+ """
+ # cs is a trimmed copy
+ [cs] = pu.as_series([cs])
+ if isinstance(x, tuple) or isinstance(x, list) :
+ x = np.asarray(x)
+
+ if len(cs) == 1 :
+ c0 = cs[0]
+ c1 = 0
+ elif len(cs) == 2 :
+ c0 = cs[0]
+ c1 = cs[1]
+ else :
+ nd = len(cs)
+ c0 = cs[-2]
+ c1 = cs[-1]
+ for i in range(3, len(cs) + 1) :
+ tmp = c0
+ nd = nd - 1
+ c0 = cs[-i] - (c1*(nd - 1))/nd
+ c1 = tmp + (c1*x*(2*nd - 1))/nd
+ return c0 + c1*x
+
+
+def legvander(x, deg) :
+ """Vandermonde matrix of given degree.
+
+ Returns the Vandermonde matrix of degree `deg` and sample points `x`.
+ This isn't a true Vandermonde matrix because `x` can be an arbitrary
+ ndarray and the Legendre polynomials aren't powers. If ``V`` is the
+ returned matrix and `x` is a 2d array, then the elements of ``V`` are
+ ``V[i,j,k] = P_k(x[i,j])``, where ``P_k`` is the Legendre polynomial
+ of degree ``k``.
+
+ Parameters
+ ----------
+ x : array_like
+ Array of points. The values are converted to double or complex
+ doubles. If x is scalar it is converted to a 1D array.
+ deg : integer
+ Degree of the resulting matrix.
+
+ Returns
+ -------
+ vander : Vandermonde matrix.
+ The shape of the returned matrix is ``x.shape + (deg+1,)``. The last
+ index is the degree.
+
+ """
+ ideg = int(deg)
+ if ideg != deg:
+ raise ValueError("deg must be integer")
+ if ideg < 0:
+ raise ValueError("deg must be non-negative")
+
+ x = np.array(x, copy=0, ndmin=1) + 0.0
+ v = np.empty((ideg + 1,) + x.shape, dtype=x.dtype)
+ # Use forward recursion to generate the entries. This is not as accurate
+ # as reverse recursion in this application but it is more efficient.
+ v[0] = x*0 + 1
+ if ideg > 0 :
+ v[1] = x
+ for i in range(2, ideg + 1) :
+ v[i] = (v[i-1]*x*(2*i - 1) - v[i-2]*(i - 1))/i
+ return np.rollaxis(v, 0, v.ndim)
+
+
+def legfit(x, y, deg, rcond=None, full=False, w=None):
+ """
+ Least squares fit of Legendre series to data.
+
+ Fit a Legendre series ``p(x) = p[0] * P_{0}(x) + ... + p[deg] *
+ P_{deg}(x)`` of degree `deg` to points `(x, y)`. Returns a vector of
+ coefficients `p` that minimises the squared error.
+
+ Parameters
+ ----------
+ x : array_like, shape (M,)
+ x-coordinates of the M sample points ``(x[i], y[i])``.
+ y : array_like, shape (M,) or (M, K)
+ y-coordinates of the sample points. Several data sets of sample
+ points sharing the same x-coordinates can be fitted at once by
+ passing in a 2D-array that contains one dataset per column.
+ deg : int
+ Degree of the fitting polynomial
+ rcond : float, optional
+ Relative condition number of the fit. Singular values smaller than
+ this relative to the largest singular value will be ignored. The
+ default value is len(x)*eps, where eps is the relative precision of
+ the float type, about 2e-16 in most cases.
+ full : bool, optional
+ Switch determining nature of return value. When it is False (the
+ default) just the coefficients are returned, when True diagnostic
+ information from the singular value decomposition is also returned.
+ w : array_like, shape (`M`,), optional
+ Weights. If not None, the contribution of each point
+ ``(x[i],y[i])`` to the fit is weighted by `w[i]`. Ideally the
+ weights are chosen so that the errors of the products ``w[i]*y[i]``
+ all have the same variance. The default value is None.
+
+ Returns
+ -------
+ coef : ndarray, shape (M,) or (M, K)
+ Legendre coefficients ordered from low to high. If `y` was 2-D,
+ the coefficients for the data in column k of `y` are in column
+ `k`.
+
+ [residuals, rank, singular_values, rcond] : present when `full` = True
+ Residuals of the least-squares fit, the effective rank of the
+ scaled Vandermonde matrix and its singular values, and the
+ specified value of `rcond`. For more details, see `linalg.lstsq`.
+
+ Warns
+ -----
+ RankWarning
+ The rank of the coefficient matrix in the least-squares fit is
+ deficient. The warning is only raised if `full` = False. The
+ warnings can be turned off by
+
+ >>> import warnings
+ >>> warnings.simplefilter('ignore', RankWarning)
+
+ See Also
+ --------
+ legval : Evaluates a Legendre series.
+ legvander : Vandermonde matrix of Legendre series.
+ polyfit : least squares fit using polynomials.
+ chebfit : least squares fit using Chebyshev series.
+ linalg.lstsq : Computes a least-squares fit from the matrix.
+ scipy.interpolate.UnivariateSpline : Computes spline fits.
+
+ Notes
+ -----
+ The solution are the coefficients ``c[i]`` of the Legendre series
+ ``P(x)`` that minimizes the squared error
+
+ ``E = \\sum_j |y_j - P(x_j)|^2``.
+
+ This problem is solved by setting up as the overdetermined matrix
+ equation
+
+ ``V(x)*c = y``,
+
+ where ``V`` is the Vandermonde matrix of `x`, the elements of ``c`` are
+ the coefficients to be solved for, and the elements of `y` are the
+ observed values. This equation is then solved using the singular value
+ decomposition of ``V``.
+
+ If some of the singular values of ``V`` are so small that they are
+ neglected, then a `RankWarning` will be issued. This means that the
+ coeficient values may be poorly determined. Using a lower order fit
+ will usually get rid of the warning. The `rcond` parameter can also be
+ set to a value smaller than its default, but the resulting fit may be
+ spurious and have large contributions from roundoff error.
+
+ Fits using Legendre series are usually better conditioned than fits
+ using power series, but much can depend on the distribution of the
+ sample points and the smoothness of the data. If the quality of the fit
+ is inadequate splines may be a good alternative.
+
+ References
+ ----------
+ .. [1] Wikipedia, "Curve fitting",
+ http://en.wikipedia.org/wiki/Curve_fitting
+
+ Examples
+ --------
+
+ """
+ order = int(deg) + 1
+ x = np.asarray(x) + 0.0
+ y = np.asarray(y) + 0.0
+
+ # check arguments.
+ if deg < 0 :
+ raise ValueError, "expected deg >= 0"
+ if x.ndim != 1:
+ raise TypeError, "expected 1D vector for x"
+ if x.size == 0:
+ raise TypeError, "expected non-empty vector for x"
+ if y.ndim < 1 or y.ndim > 2 :
+ raise TypeError, "expected 1D or 2D array for y"
+ if len(x) != len(y):
+ raise TypeError, "expected x and y to have same length"
+
+ # set up the least squares matrices
+ lhs = legvander(x, deg)
+ rhs = y
+ if w is not None:
+ w = np.asarray(w) + 0.0
+ if w.ndim != 1:
+ raise TypeError, "expected 1D vector for w"
+ if len(x) != len(w):
+ raise TypeError, "expected x and w to have same length"
+ # apply weights
+ if rhs.ndim == 2:
+ lhs *= w[:, np.newaxis]
+ rhs *= w[:, np.newaxis]
+ else:
+ lhs *= w[:, np.newaxis]
+ rhs *= w
+
+ # set rcond
+ if rcond is None :
+ rcond = len(x)*np.finfo(x.dtype).eps
+
+ # scale the design matrix and solve the least squares equation
+ scl = np.sqrt((lhs*lhs).sum(0))
+ c, resids, rank, s = la.lstsq(lhs/scl, rhs, rcond)
+ c = (c.T/scl).T
+
+ # warn on rank reduction
+ if rank != order and not full:
+ msg = "The fit may be poorly conditioned"
+ warnings.warn(msg, pu.RankWarning)
+
+ if full :
+ return c, [resids, rank, s, rcond]
+ else :
+ return c
+
+
+def legroots(cs):
+ """
+ Compute the roots of a Chebyshev series.
+
+ Return the roots (a.k.a "zeros") of the Legendre series represented by
+ `cs`, which is the sequence of the C-series' coefficients from lowest
+ order "term" to highest, e.g., [1,2,3] represents the Legendre series
+ ``P_0 + 2*P_1 + 3*P_2``.
+
+ Parameters
+ ----------
+ cs : array_like
+ 1-d array of Legendre series coefficients ordered from low to high.
+
+ Returns
+ -------
+ out : ndarray
+ Array of the roots. If all the roots are real, then so is the
+ dtype of ``out``; otherwise, ``out``'s dtype is complex.
+
+ See Also
+ --------
+ polyroots
+ chebroots
+
+ Notes
+ -----
+ Algorithm(s) used:
+
+ Remember: because the Legendre series basis set is different from the
+ "standard" basis set, the results of this function *may* not be what
+ one is expecting.
+
+ Examples
+ --------
+ >>> import numpy.polynomial as P
+ >>> import numpy.polynomial.Legendre as L
+ >>> P.polyroots((-1,1,-1,1)) # x^3 - x^2 + x - 1 has two complex roots
+ array([ -4.99600361e-16-1.j, -4.99600361e-16+1.j, 1.00000e+00+0.j])
+ >>> L.legroots((-1,1,-1,1)) # T3 - T2 + T1 - T0 has only real roots
+ array([ -5.00000000e-01, 2.60860684e-17, 1.00000000e+00])
+
+ """
+ # cs is a trimmed copy
+ [cs] = pu.as_series([cs])
+ if len(cs) <= 1 :
+ return np.array([], dtype=cs.dtype)
+ if len(cs) == 2 :
+ return np.array([-cs[0]/cs[1]])
+
+ n = len(cs) - 1
+ cs /= cs[-1]
+ cmat = np.zeros((n,n), dtype=cs.dtype)
+ cmat[1, 0] = 1
+ for i in range(1, n):
+ tmp = 2*i + 1
+ cmat[i - 1, i] = i/tmp
+ if i != n - 1:
+ cmat[i + 1, i] = (i + 1)/tmp
+ else:
+ cmat[:, i] -= cs[:-1]*(i + 1)/tmp
+ roots = la.eigvals(cmat)
+ roots.sort()
+ return roots
+
+
+#
+# Legendre series class
+#
+
+exec polytemplate.substitute(name='Legendre', nick='leg', domain='[-1,1]')
diff --git a/numpy/polynomial/tests/test_chebyshev.py b/numpy/polynomial/tests/test_chebyshev.py
index ffa8e984d..65bb877f4 100644
--- a/numpy/polynomial/tests/test_chebyshev.py
+++ b/numpy/polynomial/tests/test_chebyshev.py
@@ -339,11 +339,11 @@ class TestMisc(TestCase) :
def test_cheb2poly(self) :
for i in range(10) :
- assert_equal(ch.cheb2poly([0]*i + [1]), Tlist[i])
+ assert_almost_equal(ch.cheb2poly([0]*i + [1]), Tlist[i])
def test_poly2cheb(self) :
for i in range(10) :
- assert_equal(ch.poly2cheb(Tlist[i]), [0]*i + [1])
+ assert_almost_equal(ch.poly2cheb(Tlist[i]), [0]*i + [1])
def test_chebpts1(self):
#test exceptions
diff --git a/numpy/polynomial/tests/test_legendre.py b/numpy/polynomial/tests/test_legendre.py
new file mode 100644
index 000000000..f963bd2df
--- /dev/null
+++ b/numpy/polynomial/tests/test_legendre.py
@@ -0,0 +1,533 @@
+"""Tests for legendre module.
+
+"""
+from __future__ import division
+
+import numpy as np
+import numpy.polynomial.legendre as leg
+import numpy.polynomial.polynomial as poly
+from numpy.testing import *
+
+P0 = np.array([ 1])
+P1 = np.array([ 0, 1])
+P2 = np.array([-1, 0, 3])/2
+P3 = np.array([ 0, -3, 0, 5])/2
+P4 = np.array([ 3, 0, -30, 0, 35])/8
+P5 = np.array([ 0, 15, 0, -70, 0, 63])/8
+P6 = np.array([-5, 0, 105, 0,-315, 0, 231])/16
+P7 = np.array([ 0,-35, 0, 315, 0, -693, 0, 429])/16
+P8 = np.array([35, 0,-1260, 0,6930, 0,-12012, 0,6435])/128
+P9 = np.array([ 0,315, 0,-4620, 0,18018, 0,-25740, 0,12155])/128
+
+Plist = [P0, P1, P2, P3, P4, P5, P6, P7, P8, P9]
+
+def trim(x) :
+ return leg.legtrim(x, tol=1e-6)
+
+
+class TestConstants(TestCase) :
+
+ def test_legdomain(self) :
+ assert_equal(leg.legdomain, [-1, 1])
+
+ def test_legzero(self) :
+ assert_equal(leg.legzero, [0])
+
+ def test_legone(self) :
+ assert_equal(leg.legone, [1])
+
+ def test_legx(self) :
+ assert_equal(leg.legx, [0, 1])
+
+
+class TestArithmetic(TestCase) :
+ x = np.linspace(-1, 1, 100)
+ y0 = poly.polyval(x, P0)
+ y1 = poly.polyval(x, P1)
+ y2 = poly.polyval(x, P2)
+ y3 = poly.polyval(x, P3)
+ y4 = poly.polyval(x, P4)
+ y5 = poly.polyval(x, P5)
+ y6 = poly.polyval(x, P6)
+ y7 = poly.polyval(x, P7)
+ y8 = poly.polyval(x, P8)
+ y9 = poly.polyval(x, P9)
+ y = [y0, y1, y2, y3, y4, y5, y6, y7, y8, y9]
+
+ def test_legval(self) :
+ def f(x) :
+ return x*(x**2 - 1)
+
+ #check empty input
+ assert_equal(leg.legval([], [1]).size, 0)
+
+ #check normal input)
+ for i in range(10) :
+ msg = "At i=%d" % i
+ ser = np.zeros
+ tgt = self.y[i]
+ res = leg.legval(self.x, [0]*i + [1])
+ assert_almost_equal(res, tgt, err_msg=msg)
+
+ #check that shape is preserved
+ for i in range(3) :
+ dims = [2]*i
+ x = np.zeros(dims)
+ assert_equal(leg.legval(x, [1]).shape, dims)
+ assert_equal(leg.legval(x, [1,0]).shape, dims)
+ assert_equal(leg.legval(x, [1,0,0]).shape, dims)
+
+ def test_legadd(self) :
+ for i in range(5) :
+ for j in range(5) :
+ msg = "At i=%d, j=%d" % (i,j)
+ tgt = np.zeros(max(i,j) + 1)
+ tgt[i] += 1
+ tgt[j] += 1
+ res = leg.legadd([0]*i + [1], [0]*j + [1])
+ assert_equal(trim(res), trim(tgt), err_msg=msg)
+
+ def test_legsub(self) :
+ for i in range(5) :
+ for j in range(5) :
+ msg = "At i=%d, j=%d" % (i,j)
+ tgt = np.zeros(max(i,j) + 1)
+ tgt[i] += 1
+ tgt[j] -= 1
+ res = leg.legsub([0]*i + [1], [0]*j + [1])
+ assert_equal(trim(res), trim(tgt), err_msg=msg)
+
+ def test_legmulx(self):
+ assert_equal(leg.legmulx([0]), [0])
+ assert_equal(leg.legmulx([1]), [0,1])
+ for i in range(1, 5):
+ tmp = 2*i + 1
+ ser = [0]*i + [1]
+ tgt = [0]*(i - 1) + [i/tmp, 0, (i + 1)/tmp]
+ assert_equal(leg.legmulx(ser), tgt)
+
+ def test_legmul(self) :
+ # check values of result
+ for i in range(5) :
+ pol1 = [0]*i + [1]
+ val1 = leg.legval(self.x, pol1)
+ for j in range(5) :
+ msg = "At i=%d, j=%d" % (i,j)
+ pol2 = [0]*j + [1]
+ val2 = leg.legval(self.x, pol2)
+ pol3 = leg.legmul(pol1, pol2)
+ val3 = leg.legval(self.x, pol3)
+ assert_(len(pol3) == i + j + 1, msg)
+ assert_almost_equal(val3, val1*val2, err_msg=msg)
+
+ def test_legdiv(self) :
+ for i in range(5) :
+ for j in range(5) :
+ msg = "At i=%d, j=%d" % (i,j)
+ ci = [0]*i + [1]
+ cj = [0]*j + [1]
+ tgt = leg.legadd(ci, cj)
+ quo, rem = leg.legdiv(tgt, ci)
+ res = leg.legadd(leg.legmul(quo, ci), rem)
+ assert_equal(trim(res), trim(tgt), err_msg=msg)
+
+
+class TestCalculus(TestCase) :
+
+ def test_legint(self) :
+ # check exceptions
+ assert_raises(ValueError, leg.legint, [0], .5)
+ assert_raises(ValueError, leg.legint, [0], -1)
+ assert_raises(ValueError, leg.legint, [0], 1, [0,0])
+
+ # test integration of zero polynomial
+ for i in range(2, 5):
+ k = [0]*(i - 2) + [1]
+ res = leg.legint([0], m=i, k=k)
+ assert_almost_equal(res, [0, 1])
+
+ # check single integration with integration constant
+ for i in range(5) :
+ scl = i + 1
+ pol = [0]*i + [1]
+ tgt = [i] + [0]*i + [1/scl]
+ legpol = leg.poly2leg(pol)
+ legint = leg.legint(legpol, m=1, k=[i])
+ res = leg.leg2poly(legint)
+ assert_almost_equal(trim(res), trim(tgt))
+
+ # check single integration with integration constant and lbnd
+ for i in range(5) :
+ scl = i + 1
+ pol = [0]*i + [1]
+ legpol = leg.poly2leg(pol)
+ legint = leg.legint(legpol, m=1, k=[i], lbnd=-1)
+ assert_almost_equal(leg.legval(-1, legint), i)
+
+ # check single integration with integration constant and scaling
+ for i in range(5) :
+ scl = i + 1
+ pol = [0]*i + [1]
+ tgt = [i] + [0]*i + [2/scl]
+ legpol = leg.poly2leg(pol)
+ legint = leg.legint(legpol, m=1, k=[i], scl=2)
+ res = leg.leg2poly(legint)
+ assert_almost_equal(trim(res), trim(tgt))
+
+ # check multiple integrations with default k
+ for i in range(5) :
+ for j in range(2,5) :
+ pol = [0]*i + [1]
+ tgt = pol[:]
+ for k in range(j) :
+ tgt = leg.legint(tgt, m=1)
+ res = leg.legint(pol, m=j)
+ assert_almost_equal(trim(res), trim(tgt))
+
+ # check multiple integrations with defined k
+ for i in range(5) :
+ for j in range(2,5) :
+ pol = [0]*i + [1]
+ tgt = pol[:]
+ for k in range(j) :
+ tgt = leg.legint(tgt, m=1, k=[k])
+ res = leg.legint(pol, m=j, k=range(j))
+ assert_almost_equal(trim(res), trim(tgt))
+
+ # check multiple integrations with lbnd
+ for i in range(5) :
+ for j in range(2,5) :
+ pol = [0]*i + [1]
+ tgt = pol[:]
+ for k in range(j) :
+ tgt = leg.legint(tgt, m=1, k=[k], lbnd=-1)
+ res = leg.legint(pol, m=j, k=range(j), lbnd=-1)
+ assert_almost_equal(trim(res), trim(tgt))
+
+ # check multiple integrations with scaling
+ for i in range(5) :
+ for j in range(2,5) :
+ pol = [0]*i + [1]
+ tgt = pol[:]
+ for k in range(j) :
+ tgt = leg.legint(tgt, m=1, k=[k], scl=2)
+ res = leg.legint(pol, m=j, k=range(j), scl=2)
+ assert_almost_equal(trim(res), trim(tgt))
+
+ def test_legder(self) :
+ # check exceptions
+ assert_raises(ValueError, leg.legder, [0], .5)
+ assert_raises(ValueError, leg.legder, [0], -1)
+
+ # check that zeroth deriviative does nothing
+ for i in range(5) :
+ tgt = [1] + [0]*i
+ res = leg.legder(tgt, m=0)
+ assert_equal(trim(res), trim(tgt))
+
+ # check that derivation is the inverse of integration
+ for i in range(5) :
+ for j in range(2,5) :
+ tgt = [1] + [0]*i
+ res = leg.legder(leg.legint(tgt, m=j), m=j)
+ assert_almost_equal(trim(res), trim(tgt))
+
+ # check derivation with scaling
+ for i in range(5) :
+ for j in range(2,5) :
+ tgt = [1] + [0]*i
+ res = leg.legder(leg.legint(tgt, m=j, scl=2), m=j, scl=.5)
+ assert_almost_equal(trim(res), trim(tgt))
+
+
+class TestMisc(TestCase) :
+
+ def test_legfromroots(self) :
+ res = leg.legfromroots([])
+ assert_almost_equal(trim(res), [1])
+ for i in range(1,5) :
+ roots = np.cos(np.linspace(-np.pi, 0, 2*i + 1)[1::2])
+ pol = leg.legfromroots(roots)
+ res = leg.legval(roots, pol)
+ tgt = 0
+ assert_(len(pol) == i + 1)
+ assert_almost_equal(leg.leg2poly(pol)[-1], 1)
+ assert_almost_equal(res, tgt)
+
+ def test_legroots(self) :
+ assert_almost_equal(leg.legroots([1]), [])
+ assert_almost_equal(leg.legroots([1, 2]), [-.5])
+ for i in range(2,5) :
+ tgt = np.linspace(-1, 1, i)
+ res = leg.legroots(leg.legfromroots(tgt))
+ assert_almost_equal(trim(res), trim(tgt))
+
+ def test_legvander(self) :
+ # check for 1d x
+ x = np.arange(3)
+ v = leg.legvander(x, 3)
+ assert_(v.shape == (3,4))
+ for i in range(4) :
+ coef = [0]*i + [1]
+ assert_almost_equal(v[...,i], leg.legval(x, coef))
+
+ # check for 2d x
+ x = np.array([[1,2],[3,4],[5,6]])
+ v = leg.legvander(x, 3)
+ assert_(v.shape == (3,2,4))
+ for i in range(4) :
+ coef = [0]*i + [1]
+ assert_almost_equal(v[...,i], leg.legval(x, coef))
+
+ def test_legfit(self) :
+ def f(x) :
+ return x*(x - 1)*(x - 2)
+
+ # Test exceptions
+ assert_raises(ValueError, leg.legfit, [1], [1], -1)
+ assert_raises(TypeError, leg.legfit, [[1]], [1], 0)
+ assert_raises(TypeError, leg.legfit, [], [1], 0)
+ assert_raises(TypeError, leg.legfit, [1], [[[1]]], 0)
+ assert_raises(TypeError, leg.legfit, [1, 2], [1], 0)
+ assert_raises(TypeError, leg.legfit, [1], [1, 2], 0)
+ assert_raises(TypeError, leg.legfit, [1], [1], 0, w=[[1]])
+ assert_raises(TypeError, leg.legfit, [1], [1], 0, w=[1,1])
+
+ # Test fit
+ x = np.linspace(0,2)
+ y = f(x)
+ #
+ coef3 = leg.legfit(x, y, 3)
+ assert_equal(len(coef3), 4)
+ assert_almost_equal(leg.legval(x, coef3), y)
+ #
+ coef4 = leg.legfit(x, y, 4)
+ assert_equal(len(coef4), 5)
+ assert_almost_equal(leg.legval(x, coef4), y)
+ #
+ coef2d = leg.legfit(x, np.array([y,y]).T, 3)
+ assert_almost_equal(coef2d, np.array([coef3,coef3]).T)
+ # test weighting
+ w = np.zeros_like(x)
+ yw = y.copy()
+ w[1::2] = 1
+ y[0::2] = 0
+ wcoef3 = leg.legfit(x, yw, 3, w=w)
+ assert_almost_equal(wcoef3, coef3)
+ #
+ wcoef2d = leg.legfit(x, np.array([yw,yw]).T, 3, w=w)
+ assert_almost_equal(wcoef2d, np.array([coef3,coef3]).T)
+
+ def test_legtrim(self) :
+ coef = [2, -1, 1, 0]
+
+ # Test exceptions
+ assert_raises(ValueError, leg.legtrim, coef, -1)
+
+ # Test results
+ assert_equal(leg.legtrim(coef), coef[:-1])
+ assert_equal(leg.legtrim(coef, 1), coef[:-3])
+ assert_equal(leg.legtrim(coef, 2), [0])
+
+ def test_legline(self) :
+ assert_equal(leg.legline(3,4), [3, 4])
+
+ def test_leg2poly(self) :
+ for i in range(10) :
+ assert_almost_equal(leg.leg2poly([0]*i + [1]), Plist[i])
+
+ def test_poly2leg(self) :
+ for i in range(10) :
+ assert_almost_equal(leg.poly2leg(Plist[i]), [0]*i + [1])
+
+
+def assert_poly_almost_equal(p1, p2):
+ assert_almost_equal(p1.coef, p2.coef)
+ assert_equal(p1.domain, p2.domain)
+
+
+class TestLegendreClass(TestCase) :
+
+ p1 = leg.Legendre([1,2,3])
+ p2 = leg.Legendre([1,2,3], [0,1])
+ p3 = leg.Legendre([1,2])
+ p4 = leg.Legendre([2,2,3])
+ p5 = leg.Legendre([3,2,3])
+
+ def test_equal(self) :
+ assert_(self.p1 == self.p1)
+ assert_(self.p2 == self.p2)
+ assert_(not self.p1 == self.p2)
+ assert_(not self.p1 == self.p3)
+ assert_(not self.p1 == [1,2,3])
+
+ def test_not_equal(self) :
+ assert_(not self.p1 != self.p1)
+ assert_(not self.p2 != self.p2)
+ assert_(self.p1 != self.p2)
+ assert_(self.p1 != self.p3)
+ assert_(self.p1 != [1,2,3])
+
+ def test_add(self) :
+ tgt = leg.Legendre([2,4,6])
+ assert_(self.p1 + self.p1 == tgt)
+ assert_(self.p1 + [1,2,3] == tgt)
+ assert_([1,2,3] + self.p1 == tgt)
+
+ def test_sub(self) :
+ tgt = leg.Legendre([1])
+ assert_(self.p4 - self.p1 == tgt)
+ assert_(self.p4 - [1,2,3] == tgt)
+ assert_([2,2,3] - self.p1 == tgt)
+
+ def test_mul(self) :
+ tgt = leg.Legendre([4.13333333, 8.8, 11.23809524, 7.2, 4.62857143])
+ assert_poly_almost_equal(self.p1 * self.p1, tgt)
+ assert_poly_almost_equal(self.p1 * [1,2,3], tgt)
+ assert_poly_almost_equal([1,2,3] * self.p1, tgt)
+
+ def test_floordiv(self) :
+ tgt = leg.Legendre([1])
+ assert_(self.p4 // self.p1 == tgt)
+ assert_(self.p4 // [1,2,3] == tgt)
+ assert_([2,2,3] // self.p1 == tgt)
+
+ def test_mod(self) :
+ tgt = leg.Legendre([1])
+ assert_((self.p4 % self.p1) == tgt)
+ assert_((self.p4 % [1,2,3]) == tgt)
+ assert_(([2,2,3] % self.p1) == tgt)
+
+ def test_divmod(self) :
+ tquo = leg.Legendre([1])
+ trem = leg.Legendre([2])
+ quo, rem = divmod(self.p5, self.p1)
+ assert_(quo == tquo and rem == trem)
+ quo, rem = divmod(self.p5, [1,2,3])
+ assert_(quo == tquo and rem == trem)
+ quo, rem = divmod([3,2,3], self.p1)
+ assert_(quo == tquo and rem == trem)
+
+ def test_pow(self) :
+ tgt = leg.Legendre([1])
+ for i in range(5) :
+ res = self.p1**i
+ assert_(res == tgt)
+ tgt = tgt*self.p1
+
+ def test_call(self) :
+ # domain = [-1, 1]
+ x = np.linspace(-1, 1)
+ tgt = 3*(1.5*x**2 - .5) + 2*x + 1
+ assert_almost_equal(self.p1(x), tgt)
+
+ # domain = [0, 1]
+ x = np.linspace(0, 1)
+ xx = 2*x - 1
+ assert_almost_equal(self.p2(x), self.p1(xx))
+
+ def test_degree(self) :
+ assert_equal(self.p1.degree(), 2)
+
+ def test_trimdeg(self) :
+ assert_raises(ValueError, self.p1.cutdeg, .5)
+ assert_raises(ValueError, self.p1.cutdeg, -1)
+ assert_equal(len(self.p1.cutdeg(3)), 3)
+ assert_equal(len(self.p1.cutdeg(2)), 3)
+ assert_equal(len(self.p1.cutdeg(1)), 2)
+ assert_equal(len(self.p1.cutdeg(0)), 1)
+
+ def test_convert(self) :
+ x = np.linspace(-1,1)
+ p = self.p1.convert(domain=[0,1])
+ assert_almost_equal(p(x), self.p1(x))
+
+ def test_mapparms(self) :
+ parms = self.p2.mapparms()
+ assert_almost_equal(parms, [-1, 2])
+
+ def test_trim(self) :
+ coef = [1, 1e-6, 1e-12, 0]
+ p = leg.Legendre(coef)
+ assert_equal(p.trim().coef, coef[:3])
+ assert_equal(p.trim(1e-10).coef, coef[:2])
+ assert_equal(p.trim(1e-5).coef, coef[:1])
+
+ def test_truncate(self) :
+ assert_raises(ValueError, self.p1.truncate, .5)
+ assert_raises(ValueError, self.p1.truncate, 0)
+ assert_equal(len(self.p1.truncate(4)), 3)
+ assert_equal(len(self.p1.truncate(3)), 3)
+ assert_equal(len(self.p1.truncate(2)), 2)
+ assert_equal(len(self.p1.truncate(1)), 1)
+
+ def test_copy(self) :
+ p = self.p1.copy()
+ assert_(self.p1 == p)
+
+ def test_integ(self) :
+ p = self.p2.integ()
+ assert_almost_equal(p.coef, leg.legint([1,2,3], 1, 0, scl=.5))
+ p = self.p2.integ(lbnd=0)
+ assert_almost_equal(p(0), 0)
+ p = self.p2.integ(1, 1)
+ assert_almost_equal(p.coef, leg.legint([1,2,3], 1, 1, scl=.5))
+ p = self.p2.integ(2, [1, 2])
+ assert_almost_equal(p.coef, leg.legint([1,2,3], 2, [1,2], scl=.5))
+
+ def test_deriv(self) :
+ p = self.p2.integ(2, [1, 2])
+ assert_almost_equal(p.deriv(1).coef, self.p2.integ(1, [1]).coef)
+ assert_almost_equal(p.deriv(2).coef, self.p2.coef)
+
+ def test_roots(self) :
+ p = leg.Legendre(leg.poly2leg([0, -1, 0, 1]), [0, 1])
+ res = p.roots()
+ tgt = [0, .5, 1]
+ assert_almost_equal(res, tgt)
+
+ def test_linspace(self):
+ xdes = np.linspace(0, 1, 20)
+ ydes = self.p2(xdes)
+ xres, yres = self.p2.linspace(20)
+ assert_almost_equal(xres, xdes)
+ assert_almost_equal(yres, ydes)
+
+ def test_fromroots(self) :
+ roots = [0, .5, 1]
+ p = leg.Legendre.fromroots(roots, domain=[0, 1])
+ res = p.coef
+ tgt = leg.poly2leg([0, -1, 0, 1])
+ assert_almost_equal(res, tgt)
+
+ def test_fit(self) :
+ def f(x) :
+ return x*(x - 1)*(x - 2)
+ x = np.linspace(0,3)
+ y = f(x)
+
+ # test default value of domain
+ p = leg.Legendre.fit(x, y, 3)
+ assert_almost_equal(p.domain, [0,3])
+
+ # test that fit works in given domains
+ p = leg.Legendre.fit(x, y, 3, None)
+ assert_almost_equal(p(x), y)
+ assert_almost_equal(p.domain, [0,3])
+ p = leg.Legendre.fit(x, y, 3, [])
+ assert_almost_equal(p(x), y)
+ assert_almost_equal(p.domain, [-1, 1])
+ # test that fit accepts weights.
+ w = np.zeros_like(x)
+ yw = y.copy()
+ w[1::2] = 1
+ yw[0::2] = 0
+ p = leg.Legendre.fit(x, yw, 3, w=w)
+ assert_almost_equal(p(x), y)
+
+ def test_identity(self) :
+ x = np.linspace(0,3)
+ p = leg.Legendre.identity()
+ assert_almost_equal(p(x), x)
+ p = leg.Legendre.identity([1,3])
+ assert_almost_equal(p(x), x)