feat: add methods scaleRows and scaleColumns

Author: stropitek

package.json

@@ -55,5 +55,8 @@
     "pretty-hrtime": "^1.0.0",
     "should": "^9.0.2",
     "should-approximately-deep": "^1.1.0"
+  },
+  "dependencies": {
+    "ml-array-utils": "^0.2.4"
   }
 }

src/matrix.js

@@ -1,5 +1,7 @@
 'use strict';
 
+const arrayUtils = require('ml-array-utils');
+
 /**
  * Real matrix
  * @class Matrix
@@ -1026,6 +1028,43 @@ class Matrix extends Array {
         return result;
     }
 
+    /**
+     * Returns a row-by-row scaled matrix
+     * @param [min=0] - Minimum scaled value
+     * @param [max=1] - Maximum scaled value
+     */
+    scaleRows(min, max) {
+        min = min === undefined ? 0 : min;
+        max = max === undefined ? 1 : max;
+        var newMatrix = Matrix.empty(this.rows, this.columns);
+        for(var i=0; i<this.rows; i++) {
+            var scaled = arrayUtils.scale(this.getRow(i), {min, max});
+            newMatrix.setRow(i, scaled);
+        }
+        return newMatrix;
+    }
+
+    /**
+     * Returns a column-by-column scaled matrix
+     * @param [min=0] - Minimum scaled value
+     * @param [max=1] - Maximum scaled value
+     */
+    scaleColumns(min, max) {
+        min = min === undefined ? 0 : min;
+        max = max === undefined ? 1 : max;
+        var newMatrix = Matrix.empty(this.rows, this.columns);
+        for(var i=0; i<this.columns; i++) {
+            var scaled = arrayUtils.scale(this.getColumn(i), {
+                min: min,
+                max: max
+            });
+            newMatrix.setColumn(i, scaled);
+        }
+        return newMatrix;
+    }
+
+
+
     /**
      * Returns the Kronecker product (also known as tensor product) between this and other
      * See https://en.wikipedia.org/wiki/Kronecker_product

test/matrix/utility.js

@@ -91,4 +91,14 @@ describe('utility methods', function () {
         transpose.rows.should.equal(3);
         transpose.columns.should.equal(2);
     });
+
+    it('scale rows', function () {
+        var matrix = new Matrix([[-1,0,1],[6, 9, 7]]);
+        matrix.scaleRows().to2DArray().should.eql([[0, 1/2, 1],[0, 1, 1/3]]);
+    });
+
+    it('scale columns', function () {
+        var matrix = new Matrix([[1,2],[-5,3],[2,4]]);
+        matrix.scaleColumns().to2DArray().should.eql([[6/7, 0],[0, 1/2],[1, 1]]);
+    });
 });