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Re: I would like to average the first n columns based on duplicate values of the n+1th column [message #93708 is a reply to message #93699]

Tue, 04 October 2016 03:32

Markus Schmassmann
Messages: 129
Registered: April 2016

Senior Member

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

hope that does it, Markus

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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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