Solving Matrix Index Problem

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Zaki
Zaki on 30 Sep 2013
Edited: Stephen23 on 19 Jul 2023
is anyone here know how to solve matrix index problem in matlab?? For example the following problem :
You have a matrix for which each row is a person and the column represent the number of quarters, nickels, dimes, and pennies. What is the raw index of the person with the most money?
Note for those unfamiliar with American coins ; quarter = $ 0.25, dime = $ 0.10, nickel = $ 0.05, penny = $0.01
Example :
Input a = [1 0 0 0 ; 0 1 0 0] output b = 1
since the first person will have $ 0.25 and the second person will have only $0.05
Thanks you, i need the answer..

Accepted Answer

Azzi Abdelmalek
Azzi Abdelmalek on 30 Sep 2013
c=[0.25 0.1 0.05 0.01]
a = [1 0 0 0 ; 0 1 0 0]
[max_money,b]=max(sum(bsxfun(@times,c,a),2))
  1 Comment
Zaki
Zaki on 30 Sep 2013
Moved: Stephen23 on 19 Jul 2023
Thanks for your help

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More Answers (4)

Rahul Sharma
Rahul Sharma on 8 Feb 2020
clear all
clc
a=randi(4,3,4)
k=[0.25 0.10 0.05 0.01];
for j=1:4
for i=1:3
a(i,j)=k(j)*a(i,j)
end
end
b=max(sum(a'))
disp(b)

Rahul Sharma
Rahul Sharma on 8 Feb 2020
a=randi(4,3,4)
a(:,1)=0.25*a(:,1);
a(:,2)=0.10*a(:,2);
a(:,3)=0.05*a(:,3);
a(:,4)=0.01*a(:,4);
disp(a)
b = max(sum(a'));
disp(b)

Mohana Segaran
Mohana Segaran on 19 Jul 2023
a = [1 0 0 0; 0 1 0 0; 1 1 1 0];
b = [0.25 0.1 0.05 0.01; 0.25 0.1 0.05 0.01; 0.25 0.1 0.05 0.01];
x = dot(a,b,2);
[y z]= max(x);
z

Stephen23
Stephen23 on 19 Jul 2023
Edited: Stephen23 on 19 Jul 2023
The simple and efficient approach is to use MTIMES:
M = [1,0,0,0;0,1,0,0;0,2,1,1] % any number of rows
M = 3×4
1 0 0 0 0 1 0 0 0 2 1 1
V = [0.25;0.1;0.05;0.01]; % one column
[~,X] = max(M*V)
X = 3

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