[Numpy-discussion] Finding indices and setting values

Cliff Martin camartin at snet.net
Wed May 21 08:09:02 EDT 2003


I have a problem where I want to set values in a 2D array based on 
conditions I’ve established. The variables are the NA of the system, its 
wavelength and the correct units on the device I’m modeling. Using these 
variables I define a variable N. I set up a 512 by 512 array [x,y]. Then 
I set up a radius , r = x^2 +y^2 and ask it to give me all r’s(to the 
closest integer) <= N(the variable I’ve defined above). This gives all 
the index values in that radius and then I set all those locations to a 
value of 1. After this I do some FFT ‘s, etc. So how do I do this in 
Numerical Python without having to index through i,j steps which would 
be incredibly tedious. This works fairly well in MatLab but I want to 
port my program to Python(for lots of reasons). If you’d rather I write 
the MatLab code snippet I can do that. Thanks.

Cliff Martin

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