Re: More For Loops

[Craig Markwardt <craigmnet(at)cow.physics.wisc.edu>]

Craig Markwardt <craigmnet@cow.physics.wisc.edu> writes:

> majewski@cygnus.uwa.edu.au_stralia writes:
...
> > 	for i = 0, (DATA_size[0]/2)-1 do begin
> > 		for j = 0, DATA_size[1]-1 do begin		
> > 			Data_sets_ev[i,j] = my_data[(2*i),(2*j)]
> > 			Data_sets_od[i,j] = my_data[(2*i),(2*j+1)]
> > 		endfor
> > 	endfor
...
> 
> Keep in mind that a (2M) x N array can be thought of as a 2 x M x N
> array -- or an M x N array of pairs.  IDL can reform the first kind of
> array into the second, and then it's a simple matter of extracting
> what you want.  The "_ev" is the first of each pair, the "_od" is the
> second.
> 
> my_data = reform(my_data, 2, x_data/2, y_data, /overwrite)
> 
> data_sets_ev = my_data[0,*,*]
> data_sets_od = my_data[1,*,*]

Ah, replying to myself.  I must be getting older.  

I see now that I didn't understand the layout of your original array.
Your my_data is really a (2*M*2) x N array.  That is, the even and odd
rows are interleaved.  This is still no problem.  The revised form is:

my_data = reform(my_data,    2,   x_data/4,           2, y_data, /overwrite)
;                         pair       row   pair of rows   array

data_sets_ev = my_data[0,*,0,*]
data_sets_od = my_data[0,*,1,*]

In this case it appears that you are only interested in the first of
each pair of elements, hence the [0,...].

Craig

-- 
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Craig B. Markwardt, Ph.D.         EMAIL:    craigmnet@cow.physics.wisc.edu
Astrophysics, IDL, Finance, Derivatives | Remove "net" for better response
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