# Different variable multiplication for different columns in a MATRIX

2 views (last 30 days)
NIRBAN CHAKRABORTY on 11 Apr 2022
Answered: KuriGohan on 11 Apr 2022
Suppoose I have a (6*10) matrix name as A. Now i want to multiply the 1st 5 column with 2 and next 5 column with 3 of A matrix to develop a new B matrix. How I going to write that code of multiplication. PLease help me out in this.

Voss on 11 Apr 2022
A = randi(10,[6 10])
A = 6×10
7 5 7 3 1 2 9 8 3 6 3 3 4 8 8 1 7 9 8 2 9 1 2 5 1 1 3 1 1 5 7 7 1 7 1 3 5 10 2 10 3 7 6 10 7 8 1 6 4 3 9 10 10 9 1 6 2 7 3 4
% one way:
factor = [2*ones(1,5) 3*ones(1,5)]
factor = 1×10
2 2 2 2 2 3 3 3 3 3
B = A.*factor
B = 6×10
14 10 14 6 2 6 27 24 9 18 6 6 8 16 16 3 21 27 24 6 18 2 4 10 2 3 9 3 3 15 14 14 2 14 2 9 15 30 6 30 6 14 12 20 14 24 3 18 12 9 18 20 20 18 2 18 6 21 9 12
% another way:
factor = repelem([2 3],1,5)
factor = 1×10
2 2 2 2 2 3 3 3 3 3
B = A.*factor
B = 6×10
14 10 14 6 2 6 27 24 9 18 6 6 8 16 16 3 21 27 24 6 18 2 4 10 2 3 9 3 3 15 14 14 2 14 2 9 15 30 6 30 6 14 12 20 14 24 3 18 12 9 18 20 20 18 2 18 6 21 9 12

David Hill on 11 Apr 2022
a=randi(10,5,10);
b=a.*([ones(1,5)*2,ones(1,5)*3]);

KuriGohan on 11 Apr 2022
There is probably an easier way to do this; but this is what i would do:
a1 = a(:,1:5) .* 2;
a2 = a(:,6:end).*3;
b = vertcat(a1,a2);

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