python - Get original indices of a sorted Numpy array

Question

I have an array of distances a = np.array([20.5 ,5.3 ,60.7 ,3.0 ], 'double') and I need the indices of the sorted array (for example [3, 1, 0, 2], for a.sort()). Is there a function in Numpy to do that?

Answer 1

Yes, there's the x = numpy.argsort(a) function or x = numpy.ndarray.argsort(a) method. It does exactly what you're asking for. You can also call argsort as a method on an ndarray object like so: a.argsort().

Here's a link to the documentation: http://docs.scipy.org/doc/numpy/reference/generated/numpy.argsort.html#numpy.argsort