An example of using crammers rule or geuss elimination?

Just looking for a good example

Answer 1

[Matlab Rahool]

Crammers

A = [ ...];
b = [...]';
[nr,nc] = size(A);
x = cram_rule(A,b);
fprintf('****************\n')
for i = 1:nr
    fprintf('  x(%d) = %5.3f \n',i,x(i))
end
fprintf('****************\n')
function x = cram_rule(A,b)
[nr,nc] = size(A);
DA = det(A);
for i = 1:nr
C = A;
C(:,i) = b;
x(i) = det(C)/DA;
end

Geuss

C = ...;
[nr nc] = size(C);
xn = [1:nr]';
[xn X] = gauss_elim(nr,nc,xn,C);
fprintf('****************\n')
for i = 1:nr
fprintf('  x(%d) = %5.3f\n',xn(i),X(i))
end
fprintf('****************\n')
function [xn X] = gauss_elim(nr,nc,xn,C)
% Forward Elimination
for j = 1:nr-1
for i = j+1:nr %row 1 pivot row
C(i,:) = C(i,:) - (C(i,j)/C(j,j))*C(j,:);
end
end
% Back Substitution
for i = nr:-1:1
sm = 0;
for j = nr:-1:i+1
sm = sm +X(j)*C(i,j);
end
X(i) = [C(i,nc) - sm]/C(i,i);
end
end

Answer 2

[John D'Errico]

Don't use either of them! There are many examples of things that you might learn to use when doing homework, and in class as a student. However, the fact is you don't ever want to write that code. In virtually all cases you will be better off using the provided software to solve systems of equations.

Simple rule: NEVER write your own code to do numerical methods when code is already provided. Unless of course, you are capable of writing that same code at a fully professional level. If you need to ask this question, then you are not there.