[SciPy-User] Sort b according to histogram(a)

Arthur M. Greene amg@iri.columbia....
Wed Dec 16 14:21:12 CST 2009

This can be accomplished in a loop, but I'm hoping there is a more 
efficient way: Starting with two 1-D arrays indexed the same, e.g.,

x0,x1,x2... y0,y1,y2...

the x's are first binned normally, i.e., a set of edges is defined and 
each x that falls in a particular bin generates a count. (This can be 
accomplished using histogram.) What I then need to do though, is find 
the average value of the corresponding y's. Example:

x = (1,4,7), y = (200,100,1000), edges = (0,5,10)


counts = (2,1), ydata = (150,1000)

Size of x or y is only about 500, but the procedure needs to be repeated 
many times and looping makes the execution quite slow. I've been looking 
at np.digitize, but haven't quite figured out how this (or some other 
call I don't know) might be used to "vectorize" the process. Suggestions 



Arthur M. Greene
The International Research Institute for Climate and Society
Monell Building, 61 Route 9W, Palisades, NY  10964-8000 USA
amg at iri . columbia . edu
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