feat: add selection method and selection view

Create a new matrix (or a view) based on row and column indices
mljs · Aug 4, 2016 · 59aa861 · 59aa861
1 parent eb06410
commit 59aa861
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Showing 4 changed files with 40 additions and 38 deletions.
diff --git a/src/abstractMatrix.js b/src/abstractMatrix.js
@@ -7,6 +7,7 @@ var util = require('./util');
 var MatrixTransposeView = require('./views/transpose');
 var MatrixRowView = require('./views/row');
 var MatrixSubView = require('./views/sub');
+var MatrixSelectionView = require('./views/selection');
 
 function abstractMatrix(superCtor) {
     if (superCtor === undefined) superCtor = Object;
@@ -1157,6 +1158,25 @@ function abstractMatrix(superCtor) {
             return this;
         }
 
+        /**
+         * Return a new matrix based on a selection of rows and columns
+         * @param {Array<number>} rowIndices - The row indices to select. Order matters and an index can be more than once.
+         * @param {Array<number>} columnIndices - The column indices to select. Order matters and an index can be use more than once.
+         * @returns {Matrix} The new matrix
+         */
+        selection(rowIndices, columnIndices) {
+            var indices = util.checkIndices(this, rowIndices, columnIndices);
+            var newMatrix = new this.constructor(rowIndices.length, columnIndices.length);
+            for (var i = 0; i < indices.row.length; i++) {
+                var rowIndex = indices.row[i];
+                for (var j = 0; j < indices.column.length; j++) {
+                    var columnIndex = indices.column[j];
+                    newMatrix[i][j] = this.get(rowIndex, columnIndex);
+                }
+            }
+            return newMatrix;
+        }
+
         /**
          * Returns the trace of the matrix (sum of the diagonal elements)
          * @returns {number}
@@ -1182,8 +1202,12 @@ function abstractMatrix(superCtor) {
             return new MatrixRowView(this, row);
         }
 
-        subMatrixView(rowIndices, columnIndices, startColumn, endColumn) {
-            return new MatrixSubView(this, rowIndices, columnIndices, startColumn, endColumn);
+        subMatrixView(startRow, endRow, startColumn, endColumn) {
+            return new MatrixSubView(this, startRow, endRow, startColumn, endColumn);
+        }
+
+        selectionView(rowIndices, columnIndices) {
+            return new MatrixSelectionView(this, rowIndices, columnIndices);
         }
     }
 

diff --git a/src/views/sub.js b/src/views/sub.js
@@ -4,30 +4,20 @@ var BaseView = require('./base');
 var util = require('../util');
 
 class MatrixSubView extends BaseView {
-    constructor(matrix, rowIndices, columnIndices, startColumn, endColumn) {
-        var rowI, columnI;
-        if(typeof rowIndices === 'number') {
-            var startRow = rowIndices, endRow = columnIndices;
-            util.checkRange(matrix, startRow, endRow, startColumn, endColumn);
-            rowI = util.getRange(startRow, endRow);
-            columnI = util.getRange(startColumn, endColumn);
-        } else {
-            var indices = util.checkIndices(matrix, rowIndices, columnIndices);
-            rowI = indices.row;
-            columnI = indices.column;
-        }
-        super(matrix, rowI.length, columnI.length);
-        this.rowIndices = rowI;
-        this.columnIndices = columnI;
+    constructor(matrix, startRow, endRow, startColumn, endColumn) {
+        util.checkRange(matrix, startRow, endRow, startColumn, endColumn);
+        super(matrix, endRow - startRow + 1, endColumn - startColumn + 1);
+        this.startRow = startRow;
+        this.startColumn = startColumn;
     }
 
     set(rowIndex, columnIndex, value) {
-        this.matrix.set(this.rowIndices[rowIndex], this.columnIndices[columnIndex] , value);
+        this.matrix.set(this.startRow + rowIndex, this.startColumn + columnIndex , value);
         return this;
     }
 
     get(rowIndex, columnIndex) {
-        return this.matrix.get(this.rowIndices[rowIndex], this.columnIndices[columnIndex]);
+        return this.matrix.get(this.startRow + rowIndex, this.startColumn + columnIndex);
     }
 }
 

diff --git a/test/matrix/utility.js b/test/matrix/utility.js
@@ -124,6 +124,12 @@ describe('utility methods', function () {
         }).should.throw(/Argument out of range/);
     });
 
+    it('selection matrix', function () {
+        var matrix = new Matrix([[1, 2], [-5, 3], [2, 4]]);
+        var selMatrix = matrix.selection([2,1], [1]);
+        selMatrix.to2DArray().should.eql([[4],[3]]);
+    });
+
     it('repeat matrix', function () {
         var matrix = new Matrix([[1, 2], [3, 4]]);
         matrix.repeat().to2DArray().should.eql([[1, 2], [3, 4]]);

diff --git a/test/views/sub.js b/test/views/sub.js
@@ -5,17 +5,7 @@ var Matrix = require('../..');
 describe('Sub view', function () {
     it('should correctly remap coordinates', function () {
         var m = Matrix.ones(5, 8);
-        var msv = m.subMatrixView([1,2], [2,1]);
-
-        m.get(1, 2).should.equal(1);
-        msv.set(0, 0, 5);
-        m.get(1, 2).should.equal(5);
-
-        m.get(2,1).should.equal(1);
-        m.set(2,1, 10);
-        msv.get(1,1).should.equal(10);
-
-        msv = m.subMatrixView(3,4,6,7);
+        var msv = m.subMatrixView(3,4,6,7);
         m.get(4,7).should.equal(1);
         msv.set(1, 1, 20);
         m.get(4,7).should.equal(20);
@@ -30,13 +20,5 @@ describe('Sub view', function () {
         (function () {
             m.subMatrixView(0,1,0,2);
         }).should.throw(RangeError);
-
-        (function () {
-            m.subMatrixView([1,1,2], [0,2]);
-        }).should.throw(RangeError);
-
-        (function () {
-            m.subMatrixView([1,1,2])
-        }).should.throw(TypeError);
     });
 });