numpy.expm1 — NumPy v1.13 Manual (original) (raw)

numpy. expm1(x, /, out=None, *, where=True, casting='same_kind', order='K', dtype=None, _subok=True_[, signature, _extobj_]) = <ufunc 'expm1'>

Calculate exp(x) - 1 for all elements in the array.

Parameters: x : array_like Input values. out : ndarray, None, or tuple of ndarray and None, optional A location into which the result is stored. If provided, it must have a shape that the inputs broadcast to. If not provided or None, a freshly-allocated array is returned. A tuple (possible only as a keyword argument) must have length equal to the number of outputs. where : array_like, optional Values of True indicate to calculate the ufunc at that position, values of False indicate to leave the value in the output alone. **kwargs For other keyword-only arguments, see theufunc docs.
Returns: out : ndarray Element-wise exponential minus one: out = exp(x) - 1.

See also

log1p

log(1 + x), the inverse of expm1.

Notes

This function provides greater precision than exp(x) - 1for small values of x.

Examples

The true value of exp(1e-10) - 1 is 1.00000000005e-10 to about 32 significant digits. This example shows the superiority of expm1 in this case.

np.expm1(1e-10) 1.00000000005e-10 np.exp(1e-10) - 1 1.000000082740371e-10