feat: add isEchelonForm and isReducedEchelonForm (#84)

mljs · Feb 9, 2019 · dee2a94 · dee2a94
1 parent 5b48178
commit dee2a94
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diff --git a/src/__tests__/matrix/utility.js b/src/__tests__/matrix/utility.js
@@ -277,4 +277,16 @@ describe('utility methods', () => {
     expect(result[2][0]).toBeCloseTo(0.24390244, 5);
     expect(result[2][1]).toBeCloseTo(0.07317073, 5);
   });
+  it('isEchelonForm', () => {
+    var matrix = new Matrix([[1, 0], [0, 1]]);
+    var matrix2 = new Matrix([[2, 1], [1, 1]]);
+    expect(matrix.isEchelonForm()).toStrictEqual(true);
+    expect(matrix2.isEchelonForm()).toStrictEqual(false);
+  });
+  it('isReducedEchelonForm', () => {
+    var matrix = new Matrix([[1, 0], [0, 1]]);
+    var matrix2 = new Matrix([[1, 1], [0, 1]]);
+    expect(matrix.isReducedEchelonForm()).toStrictEqual(true);
+    expect(matrix2.isReducedEchelonForm()).toStrictEqual(false);
+  });
 });
diff --git a/src/abstractMatrix.js b/src/abstractMatrix.js
@@ -343,6 +343,67 @@ export default function AbstractMatrix(superCtor) {
       return false;
     }
 
+    /**
+          * @return true if the matrix is in echelon form
+          */
+    isEchelonForm() {
+      let i = 0;
+      let j = 0;
+      let previousColumn = -1;
+      let isEchelonForm = true;
+      let checked = false;
+      while ((i < this.rows) && (isEchelonForm)) {
+        j = 0;
+        checked = false;
+        while ((j < this.columns) && (checked === false)) {
+          if (this.get(i, j) === 0) {
+            j++;
+          } else if ((this.get(i, j) === 1) && (j > previousColumn)) {
+            checked = true;
+            previousColumn = j;
+          } else {
+            isEchelonForm = false;
+            checked = true;
+          }
+        }
+        i++;
+      }
+      return isEchelonForm;
+    }
+
+    /**
+             * @return true if the matrix is in reduced echelon form
+             */
+    isReducedEchelonForm() {
+      let i = 0;
+      let j = 0;
+      let previousColumn = -1;
+      let isReducedEchelonForm = true;
+      let checked = false;
+      while ((i < this.rows) && (isReducedEchelonForm)) {
+        j = 0;
+        checked = false;
+        while ((j < this.columns) && (checked === false)) {
+          if (this.get(i, j) === 0) {
+            j++;
+          } else if ((this.get(i, j) === 1) && (j > previousColumn)) {
+            checked = true;
+            previousColumn = j;
+          } else {
+            isReducedEchelonForm = false;
+            checked = true;
+          }
+        }
+        for (let k = j + 1; k < this.rows; k++) {
+          if (this.get(i, k) !== 0) {
+            isReducedEchelonForm = false;
+          }
+        }
+        i++;
+      }
+      return isReducedEchelonForm;
+    }
+
     /**
          * Sets a given element of the matrix. mat.set(3,4,1) is equivalent to mat[3][4]=1
          * @abstract