Magnus Lie Hetland wrote:
I have a set of limits, e.g. array([0, 35, 45, 55, 75]) and I want to use these to "classify" a set of numbers (another one-dimensional array). The "class" is the number of the first limit that is lower than or equal to the number I want to classify. E.g. I'd classify 17 as 0 and 42 as 1.
My current approach is:
sum(nums[:,NewAxis] >= lims, dim=-1)
It seems a bit unnecessary to compare each number with all the limits when O(log(n)) would suffice (the limits are ordered); or even with O(n) running time, a smarter implementation could get an average of n/2 comparisons...
Suggestions?
Try searchsorted(). Searchsorted returns the index of the first bin >= the number being classified and has O(log(n)) running time.
a=numarray.array([0, 35, 45, 55, 75]) numarray.searchsorted(a, [1,42,35]) array([1, 2, 1])
Todd