# Which function should I use to fill an ouput matrix based on information in two other matrices

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Sehrish Usman 2021 年 5 月 7 日

I want to fill up an Ouput matrix row-wise, by looking into the Index information and Data.
For example, if I have three Matrices
Index = [1 2 1; 5 4 4], Data = [12 16 10; 13 16 18; 12 11 14; 18 19 22; 23 60 17],
Now loop will start from the first row of "Index" and look into the "Data" column "1". The output for say, first two loops should be:
Output = [12 13 12; 60 19 19]
Which function should I use? Histcount, accumarray or any other?

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### 採用された回答

KSSV 2021 年 5 月 7 日
Index = [1 2 1; 5 4 4];
Data = [12 16 10; 13 16 18; 12 11 14; 18 19 22; 23 60 17] ;
Output = [12 13 12; 60 19 19] ;
iwant = zeros(size(Index)) ;
for i = 1:size(Index,1)
iwant(i,:) = Data(Index(i,:)',i) ;
end
iwant
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Sehrish Usman 2021 年 5 月 7 日
Thank you KSSV, I also just figured out that I can just mention the index to get the output like you did.

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### その他の回答 (1 件)

DGM 2021 年 5 月 7 日

This is probably not the best way to do this, but here goes.
idx = [1 2 1; 5 4 4]
D = [12 16 10; 13 16 18; 12 11 14; 18 19 22; 23 60 17]
didx = sub2ind(size(D),idx,repmat((1:size(idx,1)).',[1 size(idx,2)]));
A = D(didx)

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