numpy.expm1

numpy.expm1(x[, out])

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

Parameters :

x : array_like

Input values.

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 the formula exp(x) - 1 for 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