Sum specific rows of an array

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yinki23
yinki23 il 23 Gen 2019
Risposto: s il 23 Gen 2019
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 Commenti
yinki23
yinki23 il 23 Gen 2019
Sorry if I was unspecific.
For example, rows no.3 and no.4 both have 4 and 6 in columns no.2 and no.3. So I want to sum these 2 rows up in column 1 (1+0.8). Same with rows no.6 and no.7.
I hope this helps you understand my question.
James Tursa
James Tursa il 23 Gen 2019
Are the values in columns 2 and 3 always positive integers?

Accedi per commentare.

Risposta accettata

Andrei Bobrov
Andrei Bobrov il 23 Gen 2019
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];

Più risposte (1)

s
s il 23 Gen 2019
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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