From f79e4508b197734850887eb799192f5ee2eab512 Mon Sep 17 00:00:00 2001
From: EdwardEisenhauer <sergiusz.warga@pwr.edu.pl>
Date: Sat, 6 Mar 2021 20:58:52 +0100
Subject: [PATCH] Gauss-Jordan

---
 .../gauss_jordan_elimination.m                | 31 +++++++++++++++++++
 1 file changed, 31 insertions(+)
 create mode 100644 Direct Methods for Solving Linear Systems/gauss_jordan_elimination.m

diff --git a/Direct Methods for Solving Linear Systems/gauss_jordan_elimination.m b/Direct Methods for Solving Linear Systems/gauss_jordan_elimination.m
new file mode 100644
index 0000000..20e8543
--- /dev/null
+++ b/Direct Methods for Solving Linear Systems/gauss_jordan_elimination.m	
@@ -0,0 +1,31 @@
+function A = gauss_jordan_elimination(A)
+
+[n, m] = size(A);
+if n ~= m
+    error('Matrix is not squared!')
+end
+    
+if det(A) == 0
+    error('Matrix is not nonsingular!') 
+end
+
+A
+
+for k = 1 : n-1
+    i = k:n;
+    j = k:n;
+    A(i, j);
+    maximum = max(abs(A(i, j)), [], 'all');
+    max_idx = find(abs(A==maximum));
+    [mi, lm] = ind2sub(size(A), max_idx(1));
+    A([k mi], 1:n) = deal(A([mi k], 1:n));
+    A(1:n, [k lm]) = deal(A(1:n, [lm k]));
+    p(k) = mi;
+    q(k) = lm;
+    % Perform Gaussian elimination with the greatest pivot
+    if A(k, k) ~= 0
+        rows = k+1 : n;
+        A(rows, k) = A(rows, k)/A(k, k);
+        A(rows, rows) = A(rows, rows) - A(rows, k) * A(k, rows);
+    end
+end
\ No newline at end of file