From 41a70d45b8b103242c9ca3068c6379b1d06fabbb Mon Sep 17 00:00:00 2001
From: Ziver Koc <ziver@koc.se>
Date: Sun, 3 Dec 2017 18:14:19 +0100
Subject: [PATCH] Added identity matrix

---
 src/zutil/math/MatrixMath.java      | 16 ++++++++++++++++
 test/zutil/math/MatrixMathTest.java | 11 +++++++++++
 2 files changed, 27 insertions(+)

diff --git a/src/zutil/math/MatrixMath.java b/src/zutil/math/MatrixMath.java
index ce39dbf..a409c71 100755
--- a/src/zutil/math/MatrixMath.java
+++ b/src/zutil/math/MatrixMath.java
@@ -196,4 +196,20 @@ public class MatrixMath {
                     "matrix1 " + matrix1.length + "x" + matrix1[0].length + ", " +
                     "matrix2 " + matrix2.length + "x" + matrix2[0].length + ", ");
     }
+
+    /***********************************************************************
+     *                      Util Methods
+     **********************************************************************/
+
+    /**
+     * @return a identity matrix (n x n) where the diagonal elements have the value 1
+     */
+    public static double[][] identity(int n){
+        double[][] result = new double[n][n];
+
+        for (int i=0; i < n; ++i) {
+            result[i][i] = 1;
+        }
+        return result;
+    }
 }
diff --git a/test/zutil/math/MatrixMathTest.java b/test/zutil/math/MatrixMathTest.java
index 921535e..cf14ab2 100755
--- a/test/zutil/math/MatrixMathTest.java
+++ b/test/zutil/math/MatrixMathTest.java
@@ -80,4 +80,15 @@ public class MatrixMathTest {
     }
 
 
+
+    @Test
+    public void identity(){
+        assertArrayEquals(
+                new double[][]{{1}},
+                MatrixMath.identity(1));
+
+        assertArrayEquals(
+                new double[][]{{1,0,0,0},{0,1,0,0},{0,0,1,0},{0,0,0,1}},
+                MatrixMath.identity(4));
+    }
 }
\ No newline at end of file