| Shortcut needed [message #10367] |
Sat, 15 November 1997 00:00 |
williams
Messages: 7
Registered: March 1997
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Junior Member |
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Hi fellow IDL-users,
I have a program which runs slower than I like, and wonder if someone
could help me speed it up a bit.
My data is an array of structures, call it 'a'. One element of the
structure, call it 'n' is an integer, another is a quantity which I
want to add up, call it 'x'.
There are about 100000 elements in this array. The integer n, marks
data as being of a certain type. I want to make a new array, call it
'y', which has as its nth element the sum of all the x's which have a
n-value of n. I currently do this as follows,
for n=0, n_max do begin
y[n] = total( a[where(a.n eq n)].x )
endfor
The trouble is that the loop is slow, as for loops always are. Does
anyone out there know a better way to do this kind of sorting?
Thanks,
Daniel Williams
--
+---------------------------------------------------------+
| Daniel L. Williams | Email: williams@srl.caltech.edu |
| Space Radiation Lab | Tel: 626/395-6634 |
| Caltech 220-47 | Fax: 626/449-8676 |
| Pasadena, Ca 91125 | |
| WWW: www.srl.caltech.edu/personnel/williams.html |
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