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Re: Multi-dimensions without for loop ? [message #38762 is a reply to message #38739]

Thu, 25 March 2004 06:22

Andrea Pitacco
Messages: 3
Registered: March 2004

Junior Member

On Thu, 25 Mar 2004 11:47:31 +0100, Emmanuel Christophe
<melaneum555@yahoo.fr> wrote:

> Hi,
>
> I'm trying to optimize some IDL code, removing for loops.
>
> I'm using the mean function to get the average of each line (this is for
> the example, could be another function). From a 2 dimensional array, I
> want to remove the mean of each column.
>
> Here is a sample using a loop:
> --------------------------------
> for j=0,size-1 do begin
> vect=data[j,*]
> datac[j,*]=vect-mean(vect)
> endfor
> --------------------------------
>
> How to do it in one instruction: if i'm using something like
> 'mean(data)', i'll get the average for the whole array, and not line by
> line.

Hi Emmanuel,
I have not understood clearly if you like to have the column mean
being removed from the data column, or the row (line?) mean removed
from the data row. 'Seems more likely the first. Anyway:

In the first case you may want to try:

datac = data - Total(data,2) / (Size(data))[2] #
Replicate(1D,(Size(data))[2])

In the second:

datac = data - Total(data,1) / (Size(data))[1] ##
Replicate(1D,(Size(data))[1])

Regards, Andrea

Andrea Pitacco
University of Padova, Italy

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[Message index]

		Re: Multi-dimensions without for loop ? By: Emmanuel Christophe on Fri, 26 March 2004 07:01
		Re: Multi-dimensions without for loop ? By: Andrea Pitacco on Thu, 25 March 2004 06:22
		Re: Multi-dimensions without for loop ? By: btt on Thu, 25 March 2004 06:09
		Re: Multi-dimensions without for loop ? By: JD Smith on Fri, 26 March 2004 15:36

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