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Re: I would like to average the first n columns based on duplicate values of the n+1th column [message #93712 is a reply to message #93710]

Tue, 04 October 2016 04:35

Markus Schmassmann
Messages: 129
Registered: April 2016

Senior Member

Am 04.10.2016 um 13:23 schrieb belkaraza@web.de:
> Am Dienstag, 4. Oktober 2016 13:17:24 UTC+2 schrieb belk...@web.de:
>> Am Dienstag, 4. Oktober 2016 12:32:48 UTC+2 schrieb Markus Schmassmann:
>>> On 10/03/2016 11:05 PM, belkaraza@web.de wrote:
>>>> Can Someone help me solve this problem in IDL:
>>>> "I have a matrix with duplicate numbers in one of the columns. I
>>>> would
>>>> like to average the rows with duplicate numbers. For example, I have
>>>> duplicate values in a matrix A in column 3:
>>>> A =
>>>> 1 2 1
>>>> 4 4 2
>>>> 5 4 2
>>>> 4 5 2
>>>> 5 5 3
>>>> 10 3 3
>>>>
>>>>
>>>> B =
>>>> 1 2 1
>>>> 4.3333 4.3333 2.0000
>>>> 7.5000 4.0000 3.0000
>>>>
>>>> where each row is the average values of the duplicate rows of column 3.
>>>>
>>>> Can anyone help?"
>>>>
>>>> found here:
>>>> http://stackoverflow.com/questions/15270019/i-would-like-to- average-the-first-n-columns-based-on-duplicate-values-of-the -n1
>>>
>>> if isa(A,/integer) then begin
>>> h=histogram(A[2,*],reverse_indices=ri)
>>> idx=where(h ne 0,n)
>>> B=fltarr(3,n)
>>> for i=0,n-1 do begin
>>> if ri[idx[i]] eq ri[idx[i]+1]-1 then $
>>> B[0,i]=A[*,ri[ri[idx[i]]:ri[idx[i]+1]-1]] else $
>>> B[0,i]=mean(A[*,ri[ri[idx[i]]:ri[idx[i]+1]-1]],dim=2)
>>> endfor
>>> endif else
>>> values=A[2,uniq(A[2,*],sort(A[2,*]))]
>>> ; if A[2,*] is already sorted, A[2,uniq(A[2,*])] is sufficient there
>>> n=n_elements(values)
>>> B=fltarr(3,n)
>>> for i=0,n-1 do begin
>>> w=where(A[2,*] eq values[i],cnt)
>>> if w cnt 1 then B[0,i]=A[*,where(A[2,*] eq values[i])] else $
>>> B[0,i]=mean(A[*,where(A[2,*] eq values[i])],dim=2,/nan)
>>> endfor
>>> endelse
>> Hey, thanks for the answer. The last if loop is bugged. if w cnt 1 then B[0,i]
>> Can't see how to fix that
> Ok fixed it with "if w[cnt] eq 1 then B[0,i]"
> Again thanks alot for your help ;)
if cnt eq 1 then ...

this is to avoid errors of the following type:

IDL> print, mean([0,1,2],dim=2)
% MEAN: Illegal keyword value for DIMENSION.

but if A is an integer type array, that loop does not matter anyway

depending on whether A contains non-integer values, you can choose which
part of the outer if/then/else you want to keep

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[Message index]

		I would like to average the first n columns based on duplicate values of the n+1th column By: belkaraza on Mon, 03 October 2016 14:05
		Re: I would like to average the first n columns based on duplicate values of the n+1th column By: Markus Schmassmann on Tue, 04 October 2016 03:32
		Re: I would like to average the first n columns based on duplicate values of the n+1th column By: belkaraza on Tue, 04 October 2016 04:17
		Re: I would like to average the first n columns based on duplicate values of the n+1th column By: belkaraza on Tue, 04 October 2016 04:23
		Re: I would like to average the first n columns based on duplicate values of the n+1th column By: belkaraza on Tue, 04 October 2016 04:32
		Re: I would like to average the first n columns based on duplicate values of the n+1th column By: Markus Schmassmann on Tue, 04 October 2016 04:35
		Re: I would like to average the first n columns based on duplicate values of the n+1th column By: Helder Marchetto on Tue, 04 October 2016 05:34

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