numpy.lib.scimath.log

lib.scimath.log(x) [source]

Compute the natural logarithm of x.

Return the “principal value” (for a description of this, see numpy.log) of . For real x > 0, this is a real number (log(0) returns -inf and log(np.inf) returns inf). Otherwise, the complex principle value is returned.

Parameters

xarray_like

The value(s) whose log is (are) required.

Returns

outndarray or scalar

The log of the x value(s). If x was a scalar, so is out, otherwise an array is returned.

See also

numpy.log

Notes

For a log() that returns NAN when real x < 0, use numpy.log (note, however, that otherwise numpy.log and this log are identical, i.e., both return -inf for x = 0, inf for x = inf, and, notably, the complex principle value if x.imag != 0).

Examples

>>> np.emath.log(np.exp(1))
1.0

Negative arguments are handled “correctly” (recall that exp(log(x)) == x does not hold for real x < 0):

>>> np.emath.log(-np.exp(1)) == (1 + np.pi * 1j)
True