refactor: make sum by row or column return an array

BREAKING CHANGE:

`matrix.sum('row')` and `matrix.sum('column')` now return an array instead of a Matrix.

Author: targos

matrix.d.ts

@@ -149,7 +149,17 @@ declare module 'ml-matrix' {
     minColumnIndex(column: number): number[];
     diag(): number[];
     diagonal(): number[];
-    sum(by?: 'row' | 'column'): Matrix | number;
+
+    /**
+     * Returns the sum of all elements of the matrix.
+     */
+    sum(): number;
+    /**
+     * Returns the sum by the dimension given.
+     * @param by - sum by 'row' or 'column'.
+     */
+    sum(by: 'row' | 'column'): number[];
+
     mean(): number;
     prod(): number;
     norm(type: 'frobenius' | 'max'): number;

src/abstractMatrix.js

@@ -8,11 +8,9 @@ import {
   checkColumnIndex,
   checkColumnVector,
   checkRange,
-  checkIndices,
-  sumByRow,
-  sumByColumn,
-  sumAll
+  checkIndices
 } from './util';
+import { sumByRow, sumByColumn, sumAll } from './stat';
 import MatrixTransposeView from './views/transpose';
 import MatrixRowView from './views/row';
 import MatrixSubView from './views/sub';
@@ -949,20 +947,16 @@ export default function AbstractMatrix(superCtor) {
       return diag;
     }
 
-    /**
-     * Returns the sum by the argument given, if no argument given,
-     * it returns the sum of all elements of the matrix.
-     * @param {string} by - sum by 'row' or 'column'.
-     * @return {Matrix|number}
-     */
     sum(by) {
       switch (by) {
         case 'row':
           return sumByRow(this);
         case 'column':
           return sumByColumn(this);
-        default:
+        case undefined:
           return sumAll(this);
+        default:
+          throw new Error(`invalid option: ${by}`);
       }
     }
 

src/stat.js

@@ -0,0 +1,31 @@
+import { newArray } from './util';
+
+export function sumByRow(matrix) {
+  var sum = newArray(matrix.rows);
+  for (var i = 0; i < matrix.rows; ++i) {
+    for (var j = 0; j < matrix.columns; ++j) {
+      sum[i] += matrix.get(i, j);
+    }
+  }
+  return sum;
+}
+
+export function sumByColumn(matrix) {
+  var sum = newArray(matrix.columns);
+  for (var i = 0; i < matrix.rows; ++i) {
+    for (var j = 0; j < matrix.columns; ++j) {
+      sum[j] += matrix.get(i, j);
+    }
+  }
+  return sum;
+}
+
+export function sumAll(matrix) {
+  var v = 0;
+  for (var i = 0; i < matrix.rows; i++) {
+    for (var j = 0; j < matrix.columns; j++) {
+      v += matrix.get(i, j);
+    }
+  }
+  return v;
+}

src/util.js

@@ -1,5 +1,3 @@
-import Matrix from './matrix';
-
 /**
  * @private
  * Check that a row index is not out of bounds
@@ -140,34 +138,12 @@ export function getRange(from, to) {
   return arr;
 }
 
-export function sumByRow(matrix) {
-  var sum = Matrix.zeros(matrix.rows, 1);
-  for (var i = 0; i < matrix.rows; ++i) {
-    for (var j = 0; j < matrix.columns; ++j) {
-      sum.set(i, 0, sum.get(i, 0) + matrix.get(i, j));
-    }
-  }
-  return sum;
-}
-
-export function sumByColumn(matrix) {
-  var sum = Matrix.zeros(1, matrix.columns);
-  for (var i = 0; i < matrix.rows; ++i) {
-    for (var j = 0; j < matrix.columns; ++j) {
-      sum.set(0, j, sum.get(0, j) + matrix.get(i, j));
-    }
-  }
-  return sum;
-}
-
-export function sumAll(matrix) {
-  var v = 0;
-  for (var i = 0; i < matrix.rows; i++) {
-    for (var j = 0; j < matrix.columns; j++) {
-      v += matrix.get(i, j);
-    }
+export function newArray(length) {
+  var array = [];
+  for (var i = 0; i < length; i++) {
+    array.push(i);
   }
-  return v;
+  return array;
 }
 
 function checkNumber(name, value) {