""" Functions to operate on polynomials. """ __all__ = ['poly', 'roots', 'polyint', 'polyder', 'polyadd', 'polysub', 'polymul', 'polydiv', 'polyval', 'poly1d', 'polyfit', 'RankWarning'] import re import warnings import numpy.core.numeric as NX from numpy.core import isscalar, abs, finfo, atleast_1d, hstack from numpy.lib.twodim_base import diag, vander from numpy.lib.function_base import trim_zeros, sort_complex from numpy.lib.type_check import iscomplex, real, imag from numpy.linalg import eigvals, lstsq class RankWarning(UserWarning): """Issued by polyfit when Vandermonde matrix is rank deficient. """ pass def poly(seq_of_zeros): """ Return polynomial coefficients given a sequence of roots. Calculate the coefficients of a polynomial given the zeros of the polynomial. If a square matrix is given, then the coefficients for characteristic equation of the matrix, defined by :math:`\\mathrm{det}(\\mathbf{A} - \\lambda \\mathbf{I})`, are returned. Parameters ---------- seq_of_zeros : ndarray A sequence of polynomial roots or a square matrix. Returns ------- coefs : ndarray A sequence of polynomial coefficients representing the polynomial :math:`\\mathrm{coefs}[0] x^{n-1} + \\mathrm{coefs}[1] x^{n-2} + ... + \\mathrm{coefs}[2] x + \\mathrm{coefs}[n]` See Also -------- numpy.poly1d : A one-dimensional polynomial class. numpy.roots : Return the roots of the polynomial coefficients in p numpy.polyfit : Least squares polynomial fit Examples -------- Given a sequence of polynomial zeros, >>> b = np.roots([1, 3, 1, 5, 6]) >>> np.poly(b) array([ 1., 3., 1., 5., 6.]) Given a square matrix, >>> P = np.array([[19, 3], [-2, 26]]) >>> np.poly(P) array([ 1., -45., 500.]) """ seq_of_zeros = atleast_1d(seq_of_zeros) sh = seq_of_zeros.shape if len(sh) == 2 and sh[0] == sh[1]: seq_of_zeros = eigvals(seq_of_zeros) elif len(sh) ==1: pass else: raise ValueError, "input must be 1d or square 2d array." if len(seq_of_zeros) == 0: return 1.0 a = [1] for k in range(len(seq_of_zeros)): a = NX.convolve(a, [1, -seq_of_zeros[k]], mode='full') if issubclass(a.dtype.type, NX.complexfloating): # if complex roots are all complex conjugates, the roots are real. roots = NX.asarray(seq_of_zeros, complex) pos_roots = sort_complex(NX.compress(roots.imag > 0, roots)) neg_roots = NX.conjugate(sort_complex( NX.compress(roots.imag < 0,roots))) if (len(pos_roots) == len(neg_roots) and NX.alltrue(neg_roots == pos_roots)): a = a.real.copy() return a def roots(p): """ Return the roots of a polynomial with coefficients given in p. The values in the rank-1 array `p` are coefficients of a polynomial. If the length of `p` is n+1 then the polynomial is described by p[0] * x**n + p[1] * x**(n-1) + ... + p[n-1]*x + p[n] Parameters ---------- p : array_like of shape(M,) Rank-1 array of polynomial co-efficients. Returns ------- out : ndarray An array containing the complex roots of the polynomial. Raises ------ ValueError: When `p` cannot be converted to a rank-1 array. Examples -------- >>> coeff = [3.2, 2, 1] >>> print np.roots(coeff) [-0.3125+0.46351241j -0.3125-0.46351241j] """ # If input is scalar, this makes it an array p = atleast_1d(p) if len(p.shape) != 1: raise ValueError,"Input must be a rank-1 array." # find non-zero array entries non_zero = NX.nonzero(NX.ravel(p))[0] # Return an empty array if polynomial is all zeros if len(non_zero) == 0: return NX.array([]) # find the number of trailing zeros -- this is the number of roots at 0. trailing_zeros = len(p) - non_zero[-1] - 1 # strip leading and trailing zeros p = p[int(non_zero[0]):int(non_zero[-1])+1] # casting: if incoming array isn't floating point, make it floating point. if not issubclass(p.dtype.type, (NX.floating, NX.complexfloating)): p = p.astype(float) N = len(p) if N > 1: # build companion matrix and find its eigenvalues (the roots) A = diag(NX.ones((N-2,), p.dtype), -1) A[0, :] = -p[1:] / p[0] roots = eigvals(A) else: roots = NX.array([]) # tack any zeros onto the back of the array roots = hstack((roots, NX.zeros(trailing_zeros, roots.dtype))) return roots def polyint(p, m=1, k=None): """ Return an antiderivative (indefinite integral) of a polynomial. The returned order `m` antiderivative `P` of polynomial `p` satisfies :math:`\\frac{d^m}{dx^m}P(x) = p(x)` and is defined up to `m - 1` integration constants `k`. The constants determine the low-order polynomial part .. math:: \\frac{k_{m-1}}{0!} x^0 + \\ldots + \\frac{k_0}{(m-1)!}x^{m-1} of `P` so that :math:`P^{(j)}(0) = k_{m-j-1}`. Parameters ---------- p : {array_like, poly1d} Polynomial to differentiate. A sequence is interpreted as polynomial coefficients, see `poly1d`. m : int, optional Order of the antiderivative. (Default: 1) k : {None, list of `m` scalars, scalar}, optional Integration constants. They are given in the order of integration: those corresponding to highest-order terms come first. If ``None`` (default), all constants are assumed to be zero. If `m = 1`, a single scalar can be given instead of a list. See Also -------- polyder : derivative of a polynomial poly1d.integ : equivalent method Examples -------- The defining property of the antiderivative: >>> p = np.poly1d([1,1,1]) >>> P = np.polyint(p) poly1d([ 0.33333333, 0.5 , 1. , 0. ]) >>> np.polyder(P) == p True The integration constants default to zero, but can be specified: >>> P = np.polyint(p, 3) >>> P(0) 0.0 >>> np.polyder(P)(0) 0.0 >>> np.polyder(P, 2)(0) 0.0 >>> P = np.polyint(p, 3, k=[6,5,3]) >>> P poly1d([ 0.01666667, 0.04166667, 0.16666667, 3., 5., 3. ]) Note that 3 = 6 / 2!, and that the constants are given in the order of integrations. Constant of the highest-order polynomial term comes first: >>> np.polyder(P, 2)(0) 6.0 >>> np.polyder(P, 1)(0) 5.0 >>> P(0) 3.0 """ m = int(m) if m < 0: raise ValueError, "Order of integral must be positive (see polyder)" if k is None: k = NX.zeros(m, float) k = atleast_1d(k) if len(k) == 1 and m > 1: k = k[0]*NX.ones(m, float) if len(k) < m: raise ValueError, \ "k must be a scalar or a rank-1 array of length 1 or >m." truepoly = isinstance(p, poly1d) p = NX.asarray(p) if m == 0: if truepoly: return poly1d(p) return p else: # Note: this must work also with object and integer arrays y = NX.concatenate((p.__truediv__(NX.arange(len(p), 0, -1)), [k[0]])) val = polyint(y, m - 1, k=k[1:]) if truepoly: return poly1d(val) return val def polyder(p, m=1): """ Return the derivative of the specified order of a polynomial. Parameters ---------- p : poly1d or sequence Polynomial to differentiate. A sequence is interpreted as polynomial coefficients, see `poly1d`. m : int, optional Order of differentiation (default: 1) Returns ------- der : poly1d A new polynomial representing the derivative. See Also -------- polyint : Anti-derivative of a polynomial. poly1d : Class for one-dimensional polynomials. Examples -------- The derivative of the polynomial :math:`x^3 + x^2 + x^1 + 1` is: >>> p = np.poly1d([1,1,1,1]) >>> p2 = np.polyder(p) >>> p2 poly1d([3, 2, 1]) which evaluates to: >>> p2(2.) 17.0 We can verify this, approximating the derivative with ``(f(x + h) - f(x))/h``: >>> (p(2. + 0.001) - p(2.)) / 0.001 17.007000999997857 The fourth-order derivative of a 3rd-order polynomial is zero: >>> np.polyder(p, 2) poly1d([6, 2]) >>> np.polyder(p, 3) poly1d([6]) >>> np.polyder(p, 4) poly1d([ 0.]) """ m = int(m) truepoly = isinstance(p, poly1d) p = NX.asarray(p) n = len(p)-1 y = p[:-1] * NX.arange(n, 0, -1) if m < 0: raise ValueError, "Order of derivative must be positive (see polyint)" if m == 0: return p else: val = polyder(y, m-1) if truepoly: val = poly1d(val) return val def polyfit(x, y, deg, rcond=None, full=False): """ Least squares polynomial fit. Fit a polynomial ``p(x) = p[0] * x**deg + ... + p[deg]`` 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. Returns ------- p : ndarray, shape (M,) or (M, K) Polynomial coefficients, highest power first. If `y` was 2-D, the coefficients for `k`-th data set are in ``p[:,k]``. residuals, rank, singular_values, rcond : present only if `full` = True Residuals of the least-squares fit, the effective rank of the scaled Vandermonde coefficient matrix, 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', np.RankWarning) See Also -------- polyval : Computes polynomial values. linalg.lstsq : Computes a least-squares fit. scipy.interpolate.UnivariateSpline : Computes spline fits. Notes ----- The solution minimizes the squared error .. math :: E = \\sum_{j=0}^k |p(x_j) - y_j|^2 in the equations:: x[0]**n * p[n] + ... + x[0] * p[1] + p[0] = y[0] x[1]**n * p[n] + ... + x[1] * p[1] + p[0] = y[1] ... x[k]**n * p[n] + ... + x[k] * p[1] + p[0] = y[k] The coefficient matrix of the coefficients `p` is a Vandermonde matrix. `polyfit` issues a `RankWarning` when the least-squares fit is badly conditioned. This implies that the best fit is not well-defined due to numerical error. The results may be improved by lowering the polynomial degree or by replacing `x` by `x` - `x`.mean(). The `rcond` parameter can also be set to a value smaller than its default, but the resulting fit may be spurious: including contributions from the small singular values can add numerical noise to the result. Note that fitting polynomial coefficients is inherently badly conditioned when the degree of the polynomial is large or the interval of sample points is badly centered. The quality of the fit should always be checked in these cases. When polynomial fits are not satisfactory, splines may be a good alternative. References ---------- .. [1] Wikipedia, "Curve fitting", http://en.wikipedia.org/wiki/Curve_fitting .. [2] Wikipedia, "Polynomial interpolation", http://en.wikipedia.org/wiki/Polynomial_interpolation Examples -------- >>> x = np.array([0.0, 1.0, 2.0, 3.0, 4.0, 5.0]) >>> y = np.array([0.0, 0.8, 0.9, 0.1, -0.8, -1.0]) >>> z = np.polyfit(x, y, 3) array([ 0.08703704, -0.81349206, 1.69312169, -0.03968254]) It is convenient to use `poly1d` objects for dealing with polynomials: >>> p = np.poly1d(z) >>> p(0.5) 0.6143849206349179 >>> p(3.5) -0.34732142857143039 >>> p(10) 22.579365079365115 High-order polynomials may oscillate wildly: >>> p30 = np.poly1d(np.polyfit(x, y, 30)) /... RankWarning: Polyfit may be poorly conditioned... >>> p30(4) -0.80000000000000204 >>> p30(5) -0.99999999999999445 >>> p30(4.5) -0.10547061179440398 Illustration: >>> import matplotlib.pyplot as plt >>> xp = np.linspace(-2, 6, 100) >>> plt.plot(x, y, '.', xp, p(xp), '-', xp, p30(xp), '--') >>> plt.ylim(-2,2) >>> plt.show() """ order = int(deg) + 1 x = NX.asarray(x) + 0.0 y = NX.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 x.shape[0] != y.shape[0] : raise TypeError, "expected x and y to have same length" # set rcond if rcond is None : rcond = len(x)*finfo(x.dtype).eps # scale x to improve condition number scale = abs(x).max() if scale != 0 : x /= scale # solve least squares equation for powers of x v = vander(x, order) c, resids, rank, s = lstsq(v, y, rcond) # warn on rank reduction, which indicates an ill conditioned matrix if rank != order and not full: msg = "Polyfit may be poorly conditioned" warnings.warn(msg, RankWarning) # scale returned coefficients if scale != 0 : if c.ndim == 1 : c /= vander([scale], order)[0] else : c /= vander([scale], order).T if full : return c, resids, rank, s, rcond else : return c def polyval(p, x): """ Evaluate a polynomial at specific values. If p is of length N, this function returns the value: p[0]*(x**N-1) + p[1]*(x**N-2) + ... + p[N-2]*x + p[N-1] If x is a sequence then p(x) will be returned for all elements of x. If x is another polynomial then the composite polynomial p(x) will be returned. Parameters ---------- p : {array_like, poly1d} 1D array of polynomial coefficients from highest degree to zero or an instance of poly1d. x : {array_like, poly1d} A number, a 1D array of numbers, or an instance of poly1d. Returns ------- values : {ndarray, poly1d} If either p or x is an instance of poly1d, then an instance of poly1d is returned, otherwise a 1D array is returned. In the case where x is a poly1d, the result is the composition of the two polynomials, i.e., substitution is used. See Also -------- poly1d: A polynomial class. Notes ----- Horner's method is used to evaluate the polynomial. Even so, for polynomials of high degree the values may be inaccurate due to rounding errors. Use carefully. Examples -------- >>> np.polyval([3,0,1], 5) # 3 * 5**2 + 0 * 5**1 + 1 76 """ p = NX.asarray(p) if isinstance(x, poly1d): y = 0 else: x = NX.asarray(x) y = NX.zeros_like(x) for i in range(len(p)): y = x * y + p[i] return y def polyadd(a1, a2): """ Returns sum of two polynomials. Returns sum of polynomials; `a1` + `a2`. Input polynomials are represented as an array_like sequence of terms or a poly1d object. Parameters ---------- a1 : {array_like, poly1d} Polynomial as sequence of terms. a2 : {array_like, poly1d} Polynomial as sequence of terms. Returns ------- out : {ndarray, poly1d} Array representing the polynomial terms. See Also -------- polyval, polydiv, polymul, polyadd """ truepoly = (isinstance(a1, poly1d) or isinstance(a2, poly1d)) a1 = atleast_1d(a1) a2 = atleast_1d(a2) diff = len(a2) - len(a1) if diff == 0: val = a1 + a2 elif diff > 0: zr = NX.zeros(diff, a1.dtype) val = NX.concatenate((zr, a1)) + a2 else: zr = NX.zeros(abs(diff), a2.dtype) val = a1 + NX.concatenate((zr, a2)) if truepoly: val = poly1d(val) return val def polysub(a1, a2): """ Returns difference from subtraction of two polynomials input as sequences. Returns difference of polynomials; `a1` - `a2`. Input polynomials are represented as an array_like sequence of terms or a poly1d object. Parameters ---------- a1 : {array_like, poly1d} Minuend polynomial as sequence of terms. a2 : {array_like, poly1d} Subtrahend polynomial as sequence of terms. Returns ------- out : {ndarray, poly1d} Array representing the polynomial terms. See Also -------- polyval, polydiv, polymul, polyadd Examples -------- .. math:: (2 x^2 + 10 x - 2) - (3 x^2 + 10 x -4) = (-x^2 + 2) >>> np.polysub([2, 10, -2], [3, 10, -4]) array([-1, 0, 2]) """ truepoly = (isinstance(a1, poly1d) or isinstance(a2, poly1d)) a1 = atleast_1d(a1) a2 = atleast_1d(a2) diff = len(a2) - len(a1) if diff == 0: val = a1 - a2 elif diff > 0: zr = NX.zeros(diff, a1.dtype) val = NX.concatenate((zr, a1)) - a2 else: zr = NX.zeros(abs(diff), a2.dtype) val = a1 - NX.concatenate((zr, a2)) if truepoly: val = poly1d(val) return val def polymul(a1, a2): """ Returns product of two polynomials represented as sequences. The input arrays specify the polynomial terms in turn with a length equal to the polynomial degree plus 1. Parameters ---------- a1 : {array_like, poly1d} First multiplier polynomial. a2 : {array_like, poly1d} Second multiplier polynomial. Returns ------- out : {ndarray, poly1d} Product of inputs. See Also -------- poly, polyadd, polyder, polydiv, polyfit, polyint, polysub, polyval """ truepoly = (isinstance(a1, poly1d) or isinstance(a2, poly1d)) a1,a2 = poly1d(a1),poly1d(a2) val = NX.convolve(a1, a2) if truepoly: val = poly1d(val) return val def polydiv(u, v): """ Returns the quotient and remainder of polynomial division. The input arrays specify the polynomial terms in turn with a length equal to the polynomial degree plus 1. Parameters ---------- u : {array_like, poly1d} Dividend polynomial. v : {array_like, poly1d} Divisor polynomial. Returns ------- q : ndarray Polynomial terms of quotient. r : ndarray Remainder of polynomial division. See Also -------- poly, polyadd, polyder, polydiv, polyfit, polyint, polymul, polysub, polyval Examples -------- .. math:: \\frac{3x^2 + 5x + 2}{2x + 1} = 1.5x + 1.75, remainder 0.25 >>> x = np.array([3.0, 5.0, 2.0]) >>> y = np.array([2.0, 1.0]) >>> np.polydiv(x, y) >>> (array([ 1.5 , 1.75]), array([ 0.25])) """ truepoly = (isinstance(u, poly1d) or isinstance(u, poly1d)) u = atleast_1d(u) + 0.0 v = atleast_1d(v) + 0.0 # w has the common type w = u[0] + v[0] m = len(u) - 1 n = len(v) - 1 scale = 1. / v[0] q = NX.zeros((max(m - n + 1, 1),), w.dtype) r = u.copy() for k in range(0, m-n+1): d = scale * r[k] q[k] = d r[k:k+n+1] -= d*v while NX.allclose(r[0], 0, rtol=1e-14) and (r.shape[-1] > 1): r = r[1:] if truepoly: return poly1d(q), poly1d(r) return q, r _poly_mat = re.compile(r"[*][*]([0-9]*)") def _raise_power(astr, wrap=70): n = 0 line1 = '' line2 = '' output = ' ' while 1: mat = _poly_mat.search(astr, n) if mat is None: break span = mat.span() power = mat.groups()[0] partstr = astr[n:span[0]] n = span[1] toadd2 = partstr + ' '*(len(power)-1) toadd1 = ' '*(len(partstr)-1) + power if ((len(line2)+len(toadd2) > wrap) or \ (len(line1)+len(toadd1) > wrap)): output += line1 + "\n" + line2 + "\n " line1 = toadd1 line2 = toadd2 else: line2 += partstr + ' '*(len(power)-1) line1 += ' '*(len(partstr)-1) + power output += line1 + "\n" + line2 return output + astr[n:] class poly1d(object): """ A one-dimensional polynomial class. Parameters ---------- c_or_r : array_like Polynomial coefficients, in decreasing powers. For example, ``(1, 2, 3)`` implies :math:`x^2 + 2x + 3`. If `r` is set to True, these coefficients specify the polynomial roots (values where the polynomial evaluate to 0) instead. r : bool, optional If True, `c_or_r` gives the polynomial roots. Default is False. Examples -------- Construct the polynomial :math:`x^2 + 2x + 3`: >>> p = np.poly1d([1, 2, 3]) >>> print np.poly1d(p) 2 1 x + 2 x + 3 Evaluate the polynomial: >>> p(0.5) 4.25 Find the roots: >>> p.r array([-1.+1.41421356j, -1.-1.41421356j]) Show the coefficients: >>> p.c array([1, 2, 3]) Display the order (the leading zero-coefficients are removed): >>> p.order 2 Show the coefficient of the k-th power in the polynomial (which is equivalent to ``p.c[-(i+1)]``): >>> p[1] 2 Polynomials can be added, substracted, multplied and divided (returns quotient and remainder): >>> p * p poly1d([ 1, 4, 10, 12, 9]) >>> (p**3 + 4) / p (poly1d([ 1., 4., 10., 12., 9.]), poly1d([4])) ``asarray(p)`` gives the coefficient array, so polynomials can be used in all functions that accept arrays: >>> p**2 # square of polynomial poly1d([ 1, 4, 10, 12, 9]) >>> np.square(p) # square of individual coefficients array([1, 4, 9]) The variable used in the string representation of `p` can be modified, using the `variable` parameter: >>> p = np.poly1d([1,2,3], variable='z') >>> print p 2 1 z + 2 z + 3 Construct a polynomial from its roots: >>> np.poly1d([1, 2], True) poly1d([ 1, -3, 2]) This is the same polynomial as obtained by: >>> np.poly1d([1, -1]) * np.poly1d([1, -2]) poly1d([ 1, -3, 2]) """ coeffs = None order = None variable = None def __init__(self, c_or_r, r=0, variable=None): if isinstance(c_or_r, poly1d): for key in c_or_r.__dict__.keys(): self.__dict__[key] = c_or_r.__dict__[key] if variable is not None: self.__dict__['variable'] = variable return if r: c_or_r = poly(c_or_r) c_or_r = atleast_1d(c_or_r) if len(c_or_r.shape) > 1: raise ValueError, "Polynomial must be 1d only." c_or_r = trim_zeros(c_or_r, trim='f') if len(c_or_r) == 0: c_or_r = NX.array([0.]) self.__dict__['coeffs'] = c_or_r self.__dict__['order'] = len(c_or_r) - 1 if variable is None: variable = 'x' self.__dict__['variable'] = variable def __array__(self, t=None): if t: return NX.asarray(self.coeffs, t) else: return NX.asarray(self.coeffs) def __repr__(self): vals = repr(self.coeffs) vals = vals[6:-1] return "poly1d(%s)" % vals def __len__(self): return self.order def __str__(self): thestr = "0" var = self.variable # Remove leading zeros coeffs = self.coeffs[NX.logical_or.accumulate(self.coeffs != 0)] N = len(coeffs)-1 def fmt_float(q): s = '%.4g' % q if s.endswith('.0000'): s = s[:-5] return s for k in range(len(coeffs)): if not iscomplex(coeffs[k]): coefstr = fmt_float(real(coeffs[k])) elif real(coeffs[k]) == 0: coefstr = '%sj' % fmt_float(imag(coeffs[k])) else: coefstr = '(%s + %sj)' % (fmt_float(real(coeffs[k])), fmt_float(imag(coeffs[k]))) power = (N-k) if power == 0: if coefstr != '0': newstr = '%s' % (coefstr,) else: if k == 0: newstr = '0' else: newstr = '' elif power == 1: if coefstr == '0': newstr = '' elif coefstr == 'b': newstr = var else: newstr = '%s %s' % (coefstr, var) else: if coefstr == '0': newstr = '' elif coefstr == 'b': newstr = '%s**%d' % (var, power,) else: newstr = '%s %s**%d' % (coefstr, var, power) if k > 0: if newstr != '': if newstr.startswith('-'): thestr = "%s - %s" % (thestr, newstr[1:]) else: thestr = "%s + %s" % (thestr, newstr) else: thestr = newstr return _raise_power(thestr) def __call__(self, val): return polyval(self.coeffs, val) def __neg__(self): return poly1d(-self.coeffs) def __pos__(self): return self def __mul__(self, other): if isscalar(other): return poly1d(self.coeffs * other) else: other = poly1d(other) return poly1d(polymul(self.coeffs, other.coeffs)) def __rmul__(self, other): if isscalar(other): return poly1d(other * self.coeffs) else: other = poly1d(other) return poly1d(polymul(self.coeffs, other.coeffs)) def __add__(self, other): other = poly1d(other) return poly1d(polyadd(self.coeffs, other.coeffs)) def __radd__(self, other): other = poly1d(other) return poly1d(polyadd(self.coeffs, other.coeffs)) def __pow__(self, val): if not isscalar(val) or int(val) != val or val < 0: raise ValueError, "Power to non-negative integers only." res = [1] for _ in range(val): res = polymul(self.coeffs, res) return poly1d(res) def __sub__(self, other): other = poly1d(other) return poly1d(polysub(self.coeffs, other.coeffs)) def __rsub__(self, other): other = poly1d(other) return poly1d(polysub(other.coeffs, self.coeffs)) def __div__(self, other): if isscalar(other): return poly1d(self.coeffs/other) else: other = poly1d(other) return polydiv(self, other) def __rdiv__(self, other): if isscalar(other): return poly1d(other/self.coeffs) else: other = poly1d(other) return polydiv(other, self) def __eq__(self, other): return NX.alltrue(self.coeffs == other.coeffs) def __ne__(self, other): return NX.any(self.coeffs != other.coeffs) def __setattr__(self, key, val): raise ValueError, "Attributes cannot be changed this way." def __getattr__(self, key): if key in ['r', 'roots']: return roots(self.coeffs) elif key in ['c','coef','coefficients']: return self.coeffs elif key in ['o']: return self.order else: try: return self.__dict__[key] except KeyError: raise AttributeError("'%s' has no attribute '%s'" % (self.__class__, key)) def __getitem__(self, val): ind = self.order - val if val > self.order: return 0 if val < 0: return 0 return self.coeffs[ind] def __setitem__(self, key, val): ind = self.order - key if key < 0: raise ValueError, "Does not support negative powers." if key > self.order: zr = NX.zeros(key-self.order, self.coeffs.dtype) self.__dict__['coeffs'] = NX.concatenate((zr, self.coeffs)) self.__dict__['order'] = key ind = 0 self.__dict__['coeffs'][ind] = val return def __iter__(self): return iter(self.coeffs) def integ(self, m=1, k=0): """ Return an antiderivative (indefinite integral) of this polynomial. Refer to `polyint` for full documentation. See Also -------- polyint : equivalent function """ return poly1d(polyint(self.coeffs, m=m, k=k)) def deriv(self, m=1): """ Return a derivative of this polynomial. Refer to `polyder` for full documentation. See Also -------- polyder : equivalent function """ return poly1d(polyder(self.coeffs, m=m)) # Stuff to do on module import warnings.simplefilter('always',RankWarning)