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Search found 4 results on 1 pages for 'perimosocordiae'.

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• Mapping functions of 2D numpy arrays

  - by perimosocordiae

  I have a function foo that takes a NxM numpy array as an argument and returns a scalar value. I have a AxNxM numpy array data, over which I'd like to map foo to give me a resultant numpy array of length A. Curently, I'm doing this: result = numpy.array([foo(x) for x in data]) It works, but it seems like I'm not taking advantage of the numpy magic (and speed). Is there a better way? I've looked at numpy.vectorize, and numpy.apply_along_axis, but neither works for a function of 2D arrays. EDIT: I'm doing boosted regression on 24x24 image patches, so my AxNxM is something like 1000x24x24. What I called foo above applies a Haar-like feature to a patch (so, not terribly computationally intensive).

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• Idiomatic Python: 'times' loop

  - by perimosocordiae

  Say I have a function foo that I want to call n times. In Ruby, I would write: n.times { foo } In Python, I could write: for _ in xrange(n): foo() But that seems like a hacky way of doing things. My question: Is there an idiomatic way of doing this in Python?

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• Sorting a 2D numpy array by multiple axes

  - by perimosocordiae

  I have a 2D numpy array of shape (N,2) which is holding N points (x and y coordinates). For example: array([[3, 2], [6, 2], [3, 6], [3, 4], [5, 3]]) I'd like to sort it such that my points are ordered by x-coordinate, and then by y in cases where the x coordinate is the same. So the array above should look like this: array([[3, 2], [3, 4], [3, 6], [5, 3], [6, 2]]) If this was a normal Python list, I would simply define a comparator to do what I want, but as far as I can tell, numpy's sort function doesn't accept user-defined comparators. Any ideas?

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• Storing a type in C++

  - by perimosocordiae

  Is it possible to store a type name as a C++ variable? For example, like this: type my_type = int; // or string, or Foo, or any other type void* data = ...; my_type* a = (my_type*) data; I know that 99.9% of the time there's a better way to do what you want without resorting to casting void pointers, but I'm curious if C++ allows this sort of thing.

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