# Using MATLAB to implement Cramer's Rule

1. May 29, 2005

### .....

Hi all, I'm trying to write an m-file which will compute a solution matrix given a coefficient matrix and right hand side vector using cramer's rule.. which is no problem for a specified size matrix.. but is it possible to write an m-file which computes the solution when ANY square coefficient matrix and it's right hand side vector is entered?

I guess you would need some kind of loop... but i'm not sure how to write the code to have matlab substitute the right hand side vector for a different column in the co-efficient matrix for each term...

any suggestions?

2. Oct 7, 2009

### xxacefirexx

I am curious about how to do this also...

some ideas would be really helpful.

3. Oct 7, 2009

### ApexOfDE

you just need for loop and det function to solve :|

4. Oct 8, 2009

### trambolin

here is a row/column selector the rest is looping and det function. r and c is the number of row/column that you cancel of the matrix A, Ac is the result that you get.

Code (Text):

function [Ac] = cancelrowcol(A,r,c)
[n,m] = size(A);

% Shortcut to upper left and lower right corner...
if ((r == 1) && (c ==1))
Ac = sel(A,2:n,2:m);
return
elseif ((r == n) && (c == m))
Ac = sel(A,1:n-1,1:m-1);
return
% Otherwise
else
Atemp = vertcat(sel(A,1:(r-1),1:m),sel(A,(r+1):n,1:m));
Ac = horzcat(sel(Atemp,1:(r-1),1:(c-1)),sel(Atemp,1:(r-1),(c+1:m)));
end
end