2009/5/18 Stéfan van der Walt :

2009/5/18 rob steed :

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This works fine. However, if the arrays have different lengths, we get a problem.

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y2=N.array([0,0,0,1]) N.correlate(x,y2,'full')

This looks like a bug to me.

In [54]: N.correlate([1, 0, 0, 0], [0, 0, 0, 1],'full') Out[54]: array([1, 0, 0, 0, 0, 0, 0])

In [55]: N.correlate([1, 0, 0, 0, 0], [0, 0, 0, 1],'full') Out[55]: array([1, 0, 0, 0, 0, 0, 0, 0])

In [56]: N.correlate([1, 0, 0, 0, 0], [0, 0, 0, 0, 1],'full') Out[56]: array([1, 0, 0, 0, 0, 0, 0, 0, 0])

In [57]: N.correlate([1, 0, 0, 0, 0], [0, 0, 0, 0, 0, 1],'full') Out[57]: array([0, 0, 0, 0, 0, 0, 0, 0, 0, 1])

comparing with scipy: signal.correlate behaves the same "flipping" way as np.correlate, ndimage.correlate keeps the orientation.

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np.correlate([1, 2, 0, 0, 0], [0, 0, 1, 0, 0,0],'same') array([0, 0, 0, 2, 1, 0]) np.correlate([1, 2, 0, 0, 0], [0, 0, 1, 0, 0],'same') array([1, 2, 0, 0, 0]) np.correlate([1, 2, 0, 0, 0], [0, 0, 1, 0, 0, 0],'full') array([0, 0, 0, 0, 0, 2, 1, 0, 0, 0]) np.correlate([1, 2, 0, 0, 0], [0, 0, 1, 0, 0],'full') array([0, 0, 1, 2, 0, 0, 0, 0, 0])

signal.correlate([1, 2, 0, 0, 0], [0, 0, 1, 0, 0, 0]) array([0, 0, 0, 0, 0, 2, 1, 0, 0, 0]) signal.correlate([1, 2, 0, 0, 0], [0, 0, 1, 0, 0]) array([0, 0, 1, 2, 0, 0, 0, 0, 0]) ndimage.filters.correlate([1, 2, 0, 0, 0], [0, 0, 1, 0, 0, 0],mode='constant') array([0, 1, 2, 0, 0]) ndimage.filters.correlate([1, 2, 0, 0, 0], [0, 0, 1, 0, 0],mode='constant') array([1, 2, 0, 0, 0])

Josef