How to run a function for multiple input matrices?

Hello,

Below is a code for swapping rows in a matrix to make it into diagonally dominant form.

A = [2 7 1 1 2; -1 -3 2 -23 2; 13 1 3 4 1; 1 2 -6 0 1; 1 -1 -2 3 -11];
B = [1 10 3; 2 1 8; 15 -5 3]

function makeDD(A)
%I originally put A = [2 7 1 1 2; -1 -3 2 -23 2; 13 1 3 4 1; 1 2 -6 0 1; 1 -1 -2 3 -11] here 
% but I would like to make it work % for multiple matrices.
  % test to see if a valid permutation exists
  [maxrow,maxind] = max(abs(A),[],2);
  
  if all(maxrow > (sum(abs(A),2) - maxrow)) 
    
    A(maxind,:) = A;
  end
DD_A = A
end

How can I make it work so that it can have multiple inputs or is it easiest to just have 2 functions one after the other and if so how can i make it so that they work in succession?

And how do i store the answer matrices with the names DD_A and DD_B?

Thanks in advance for any help, I been trying for ages to figure this out.

Answer 1

[Geoff Hayes]

jack - just call the function twice and store the output in separate variables or in a cell array. You will need to change your function signature so that it returns a matrix

function [DD] = makeDD(A)
% I originally put A = [2 7 1 1 2; -1 -3 2 -23 2; 13 1 3 4 1; 1 2 -6 0 1; 1 -1 -2 3 -11] here 
% but I would like to make it work % for multiple matrices.
% test to see if a valid permutation exists
[maxrow,maxind] = max(abs(A),[],2);
if all(maxrow > (sum(abs(A),2) - maxrow)) 
    A(maxind,:) = A;
end
DD = A;

Then in the command line (or from another script) just do

A = [2 7 1 1 2; -1 -3 2 -23 2; 13 1 3 4 1; 1 2 -6 0 1; 1 -1 -2 3 -11];
B = [1 10 3; 2 1 8; 15 -5 3];
C = cell(2,1);
C{1} = makeDD(A);
C{2} = makeDD(B);

[jack brown]

I still cannot get it to work

Command window:

 A = [2 7 1 1 2; -1 -3 2 -23 2; 13 1 3 4 1; 1 2 -6 0 1; 1 -1 -2 3 -11];
B = [1 10 3; 2 1 8; 15 -5 3];
C = [1 13 2; 1 3 9; -12 2 -1];
D = cell(3,1);

C{1} = makeDD(A);
C{2} = makeDD(B);
C{3} = makeDD(C);

function [DD] = makeDD(A)

% test to see if a valid permutation exists
[maxrow,maxind] = max(abs(A),[],2);
if all(maxrow > (sum(abs(A),2) - maxrow)) 
    A(maxind,:) = A;
end
DD = A;

I need the answers to be in the form DD_A= [...] DD_B=[...] etc.

What is it that i'm doing wrong? (This is my first year doing matlab which is probably obvious)

[Geoff Hayes]

jack - from your code

D = cell(3,1);
C{1} = makeDD(A);
C{2} = makeDD(B);
C{3} = makeDD(C);

D is the cell array, so you should be doing

D = cell(3,1);
D{1} = makeDD(A);
D{2} = makeDD(B);
D{3} = makeDD(C);

However, if you really need to have separate variables for each with names like DD_, then just do

DD_A = makeDD(A);
DD_B = makeDD(B);
DD_C = makeDD(C);