How to raise a numpy array to a power? (corresponding to repeated matrix multiplications, not elementwise)

Question

I want to raise a 2-dimensional numpy array, let\'s call it A, to the power of some number n, but I have thus far failed to find the funct

Answer 1

The opencv function cvPow seems to be about 3-4 times faster on my computer when raising to a rational number. Here is a sample function (you need to have the pyopencv module installed):

import pyopencv as pycv
import numpy
def pycv_power(arr, exponent):
    """Raise the elements of a floating point matrix to a power. 
    It is 3-4 times faster than numpy's built-in power function/operator."""
    if arr.dtype not in [numpy.float32, numpy.float64]:
        arr = arr.astype('f')
    res = numpy.empty_like(arr)
    if arr.flags['C_CONTIGUOUS'] == False:
        arr = numpy.ascontiguousarray(arr)        
    pycv.pow(pycv.asMat(arr), float(exponent), pycv.asMat(res))
    return res