MATLAB Answers

sum of row in pattern

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ANAND ASP on 28 Nov 2020
Edited: Adam Danz on 28 Nov 2020
Data= [ 1 4 0.0000;
2 7 0.0000;
3 9 0.0000;
4 5 0.1760;
4 6 0.1580;
5 7 0.3060;
6 9 0.3580;
7 8 0.1490;
8 9 0.2090]
i expect answer like this, its nothing but the similar vaule in 1st and 2nd column according to that sum of 3rd column
ANS= 1 0.0000
2 0.0000
3 0.0000
4 0.3340
5 0.4820
6 0.5160
7 0.4550
8 0.3580
9 0.5670
ex.: take number 4 => 0.0000 + 0.1760 + 0.1580 = 0.3340
take number 7 => 0.0000 + 0.3060 + 0.1490 = 0.4550

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Answers (4)

David Hill on 28 Nov 2020
k=unique(Data(:,1:2));
y=zeros(length(k),2);
for m=1:length(k)
y(m,:)=[k(m),sum(Data(logical(ismember(Data(:,1),k(m))+ismember(Data(:,2),k(m))),3))];
end

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Image Analyst on 28 Nov 2020
Try this:
Data = [ 1 4 0.0000;
2 7 0.0000;
3 9 0.0000;
4 5 0.1760;
4 6 0.1580;
5 7 0.3060;
6 9 0.3580;
7 8 0.1490;
8 9 0.2090]
col3 = Data(:, 3)
for row = 1 : max(max(Data(:, 1:2)))
rowsToUse = any(Data(:, 1:2) == row, 2)
theSums(row) = sum(col3(rowsToUse))
end

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Stephen Cobeldick on 28 Nov 2020
Edited: Stephen Cobeldick on 28 Nov 2020
Data = [1,4,0.0000;
2,7,0.0000;
3,9,0.0000;
4,5,0.1760;
4,6,0.1580;
5,7,0.3060;
6,9,0.3580;
7,8,0.1490;
8,9,0.2090];
[U,~,X] = unique(Data(:,1:2));
Y = [Data(:,3);Data(:,3)];
Z = [U,accumarray(X,Y)]
Z = 9×2
1.0000 0 2.0000 0 3.0000 0 4.0000 0.3340 5.0000 0.4820 6.0000 0.5160 7.0000 0.4550 8.0000 0.3580 9.0000 0.5670

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Adam Danz on 28 Nov 2020
Edited: Adam Danz on 28 Nov 2020
Data= [ 1 4 0.0000;
2 7 0.0000;
3 9 0.0000;
4 5 0.1760;
4 6 0.1580;
5 7 0.3060;
6 9 0.3580;
7 8 0.1490;
8 9 0.2090];
Fastest method (so far)
D = [Data(:,[1,3]);Data(:,[2,3])];
out = [unique(D(:,1)),accumarray(D(:,1),D(:,2))]
out = 9×2
1.0000 0 2.0000 0 3.0000 0 4.0000 0.3340 5.0000 0.4820 6.0000 0.5160 7.0000 0.4550 8.0000 0.3580 9.0000 0.5670
Slowest (1-line challenge)
out = [unique(Data(:,1:2)), arrayfun(@(i)sum(Data(any(Data(:,1:2)==i,2),3)), unique(Data(:,1:2)))]
out = 9×2
1.0000 0 2.0000 0 3.0000 0 4.0000 0.3340 5.0000 0.4820 6.0000 0.5160 7.0000 0.4550 8.0000 0.3580 9.0000 0.5670
Comparison of 10,000 iterations between existing solutions.

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