expm1(x, /, out=None, *, where=True, casting='same_kind', order='K', dtype=None, subok=True[, signature, extobj]) = <ufunc 'expm1'>¶
exp(x) - 1for all elements in the array.
- x : array_like
- 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
This condition is broadcast over the input. At locations where the condition is True, the out array will be set to the ufunc result. Elsewhere, the out array will retain its original value. Note that if an uninitialized out array is created via the default
out=None, locations within it where the condition is False will remain uninitialized.
For other keyword-only arguments, see the ufunc docs.
- out : ndarray or scalar
Element-wise exponential minus one:
out = exp(x) - 1. This is a scalar if x is a scalar.
log(1 + x), the inverse of expm1.
This function provides greater precision than
exp(x) - 1for small values of
The true value of
exp(1e-10) - 1is
1.00000000005e-10to 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