# multiply values in different rows

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Berfin Çetinkaya on 25 May 2022
Commented: DGM on 25 May 2022
Hi!
I have three matrices.
first matrices :
A=
2 3 1 4
8 5 2 3
1 2 6 7
6 8 4 1
B=
0,1
0,5
0,4
0,2
C=
10
20
15
5
25
15
10
20
For example, look at the value in the first matrix for the cell that says 8 in matrix A. For example, it says 2 on top of 8. Since it writes 2, let it take the value of the 2nd row in B matrix. (A value of 0.5 is taken.)
Since 8 is written in matrix A, take the value written in 8th row from matrix C. (It takes the value 20.)
And multiply the received value of 0.5 by the value of 20.
Let it do this for all cells in matrix A.
new matrices=
10 10 2 3
5 8 1,5 2
7,5 8 0,5 2
Thank you for help.

DGM on 25 May 2022
I'm going to guess that this is what you're after:
A = [2 3 1 4; 8 5 2 3; 1 2 6 7; 6 8 4 1];
B = [0.1; 0.5; 0.4; 0.2];
C = [10; 20; 15; 5; 25; 15; 10; 20];
output = B(A(1,:)).' .* C(A(2:end,:))
output = 3×4
10.0000 10.0000 2.0000 3.0000 5.0000 8.0000 1.5000 2.0000 7.5000 8.0000 0.5000 2.0000
##### 2 CommentsShow 1 older commentHide 1 older comment
DGM on 25 May 2022
I'm not sure what determines the number of output rows, but assuming it's 4:
A = [2 3 1 4; 8 5 2 3; 1 2 6 7; 6 8 4 1];
B = [0.1; 0.5; 0.4; 0.2];
C = [10; 20; 15; 5; 25; 15; 10; 20];
output = B(A(1,:)).*C(A(1,:));
output = repmat(output.',[4 1])
output = 4×4
10 6 1 1 10 6 1 1 10 6 1 1 10 6 1 1