Sum specific rows of an array
显示 更早的评论
Hi,
I have an array like:
0.2 2 3
1 3 4
1 4 6
0.8 4 6
2 5 1
1 6 2
0.4 6 2
Now I want to code that MATLAB sums up the values of the 1st column in the rows where the value of the 2nd and 3rd column match.
So the result should look like this below:
0.2 2 3
1 3 4
1.8 4 6
2 5 1
1.4 6 2
I hope someone can help me, thank you!
3 个评论
Bob Thompson
2019-1-23
"where the value of the 2nd and 3rd column match."
How do the values of the 2nd and 3rd column match in any of these rows?
In general form this should be fairly easy with logic indexing.
yinki23
2019-1-23
James Tursa
2019-1-23
Are the values in columns 2 and 3 always positive integers?
采纳的回答
Andrei Bobrov
2019-1-23
A = [0.2 2 3
1 3 4
1 4 6
0.8 4 6
2 5 1
1 6 2
0.4 6 2];
[a,~,c] = unique(A(:,2:3),'rows','stable');
out = [accumarray(c,A(:,1)),a];
更多回答（1 个）
s
2019-1-23
clc;
clear all;
A = [0.2 2 3;1 3 4;1 4 6;0.8 4 6;2 5 1;1 6 2;0.4 6 2];
B = size (A,1);
Result = [];
n = 0;
for i = 1:1:B-1
if (A(i,2) == A(i+1,2) && A(i,3) == A(i+1,3))
n = n+1;
end
end
for j = 1:1:B-n
if (A(j,2) == A(j+1,2) && A(j,3) == A(j+1,3))
Sum = A(j,1)+A(j+1,1);
Result = [Result; Sum A(j,2) A(j,3)]
A([j+1],:) = [];
else
Result = [Result; A(j,1) A(j,2) A(j,3)]
end
end
This should help
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