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Re: Another simple one [message #55073 is a reply to message #55061]

Sun, 29 July 2007 12:39

MarioIncandenza
Messages: 231
Registered: February 2005

Senior Member

On Jul 28, 12:58 am, snudge42 <snudg...@gmail.com> wrote:
> How do I truncate a multidimensional array at a different place for
> each dimension i.e. I start with 3x6 array of values A=
>
> 0 0 0
> 0 0 0
> 0 0 0
> 0 0 0
> 0 0 0
> 0 0 0
>
> and want to truncate each dimension at a fixed value stored in an
> array B, where the values are (2,3,4) for example so that I get:
>
> 0 0 0
> 0 0 0
> 0 0 0
> 0 0
> 0
>

By 'truncate', you mean either "perform calculations on only part of
array A" or "write output of only part of array A". For the second
case, the I/O penalty is far greater than the for-loop penalty, just
use a loop. For the first case, consider this:
;NOTE: this example truncates along rows, you'll need to TRANSPOSE to
do columns
btrunc=a*0; initialize truncation helper array
for i=0l,n_elements(b)-1 do btrunc[0]=(lindgen(b[i]+1))+1 gt 0; anyone
care to try getting rid of this loop?
print,trunc
> 1 1 1 0 0
> 1 1 1 1 0
> 1 1 1 1 1
; from here, you can manipulate A in several ways:
; such as setting truncated components to NaN:
ftrunc=where(trunc eq 0)
anew=a & anew[ftrunc]=!values.NaN
; setting truncated components to 0:
anew= a * btrunc;

Hope this helps,

--Edward H.

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[Message index]

		Re: Another simple one By: Jean H. on Mon, 30 July 2007 09:19
		Re: Another simple one By: MarioIncandenza on Sun, 29 July 2007 12:39
		Re: Another simple one By: Brian Larsen on Sat, 28 July 2007 07:14
		Re: Another simple one By: Carsten Lechte on Sat, 28 July 2007 06:19
		Re: Another simple one By: Brian Larsen on Sat, 28 July 2007 05:45
		Re: Another simple one By: snudge42 on Wed, 08 August 2007 21:43

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