diff options
Diffstat (limited to 'numpy/lib/function_base.py')
| -rw-r--r-- | numpy/lib/function_base.py | 22 |
1 files changed, 9 insertions, 13 deletions
diff --git a/numpy/lib/function_base.py b/numpy/lib/function_base.py index fabb87adc..9690c305f 100644 --- a/numpy/lib/function_base.py +++ b/numpy/lib/function_base.py @@ -3070,10 +3070,13 @@ def i0(x): See Also -------- - scipy.special.iv, scipy.special.ive + scipy.special.i0, scipy.special.iv, scipy.special.ive Notes ----- + The scipy implementation is recommended over this function: it is a + proper ufunc written in C, and more than an order of magnitude faster. + We use the algorithm published by Clenshaw [1]_ and referenced by Abramowitz and Stegun [2]_, for which the function domain is partitioned into the two intervals [0,8] and (8,inf), and Chebyshev @@ -3093,21 +3096,14 @@ def i0(x): Examples -------- - >>> np.i0([0.]) - array(1.0) # may vary + >>> np.i0(0.) + array(1.0) # may vary >>> np.i0([0., 1. + 2j]) - array([ 1.00000000+0.j , 0.18785373+0.64616944j]) # may vary + array([ 1.00000000+0.j , 0.18785373+0.64616944j]) # may vary """ - x = atleast_1d(x).copy() - y = empty_like(x) - ind = (x < 0) - x[ind] = -x[ind] - ind = (x <= 8.0) - y[ind] = _i0_1(x[ind]) - ind2 = ~ind - y[ind2] = _i0_2(x[ind2]) - return y.squeeze() + x = np.abs(x) + return piecewise(x, [x <= 8.0], [_i0_1, _i0_2]) ## End of cephes code for i0 |