numpy.log1p(x, /, out=None, *, where=True, casting='same_kind', order='K', dtype=None, subok=True[, signature, extobj]) = <ufunc 'log1p'>
Return the natural logarithm of one plus the input array, element-wise.
log(1 + x).
For real-valued input,
log1p is accurate also for
x so small that
1 + x == 1 in floating-point accuracy.
Logarithm is a multivalued function: for each
x there is an infinite number of
z such that
exp(z) = 1 + x. The convention is to return the
z whose imaginary part lies in
For real-valued input data types,
log1p always returns real output. For each value that cannot be expressed as a real number or infinity, it yields
nan and sets the
invalid floating point error flag.
For complex-valued input,
log1p is a complex analytical function that has a branch cut
[-inf, -1] and is continuous from above on it.
log1p handles the floating-point negative zero as an infinitesimal negative number, conforming to the C99 standard.
|||M. Abramowitz and I.A. Stegun, “Handbook of Mathematical Functions”, 10th printing, 1964, pp. 67. http://www.math.sfu.ca/~cbm/aands/|
|||Wikipedia, “Logarithm”. https://en.wikipedia.org/wiki/Logarithm|
>>> np.log1p(1e-99) 1e-99 >>> np.log(1 + 1e-99) 0.0
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