matrixmath - npm Package Compare versions

Comparing version 2.2.0 to 2.2.1

Matrix.js

@@ -621,5 +621,23 @@ /**
 
+  // Simple solution for 2x2 matrices
+  if (numRows === 2) {
+    var determinant = this.getDeterminant();
+    if (determinant === 0) return this;
+
+    var invertedDeterminant = 1 / determinant;
+    var m0 = invertedDeterminant * this[3];
+    var m1 = invertedDeterminant * -this[1];
+    var m2 = invertedDeterminant * -this[2];
+    var m3 = invertedDeterminant * this[0];
+    this[0] = m0;
+    this[1] = m1;
+    this[2] = m2;
+    this[3] = m3;
+
+    return this;
+  }
+
   // By using a cache, only the first call to invert will cause a memory increase.
   var cache = this._cache || (this._cache = {});
-  var matrixOfMinors = cache.matrixOfMinors || (cache.matrixOfMinors = new Matrix(numRows, numCols, false));
+  var matrixOfCoFactors = cache.matrixOfCoFactors || (cache.matrixOfCoFactors = new Matrix(numRows, numCols, false));
   var matrix = cache.tempMatrix || (cache.tempMatrix = new Matrix(this.rows, this.cols, false));
@@ -648,6 +666,14 @@
 
-      // Set the determinant in the correct position in the matrix of minors.
-      // Every other position is multiplied by -1 to get a matrix of cofactors.
-      matrixOfMinors[row * matrixOfMinors.cols + col] = (i % 2 ? -1 : 1) * matrix.getDeterminant();
+      // Some of the determinants need to change sign to become the cofactor.
+      // This is applied as a checkerboard to the matrix.
+      var coFactor = matrix.getDeterminant();
+      var rowAlternate = row % 2 === 1;
+      var colAlternate = col % 2 === 1;
+      if ((rowAlternate && !colAlternate) || (colAlternate && !rowAlternate)) {
+        coFactor *= -1;
+      }
 
+      // Set the cofactor in the correct position in the matrix of cofactors.
+      matrixOfCoFactors[row * matrixOfCoFactors.cols + col] = coFactor;
+
       i++;
@@ -661,3 +687,3 @@ }
   for (var n = 0; n < numCols; n++) {
-    originalDeterminant += this[n] * matrixOfMinors[n];
+    originalDeterminant += this[n] * matrixOfCoFactors[n];
   }
@@ -668,8 +694,8 @@
 
-  // Transpose the cofactor matrix of minors to get the adjugate matrix
-  matrixOfMinors.transpose();
+  // Transpose the cofactor of cofactors to get the adjugate matrix
+  matrixOfCoFactors.transpose();
 
-  // Multiply the matrix of minors with the inverse of the determinant,
+  // Multiply the matrix of cofactors with the inverse of the determinant,
   // to get the final inverse of the original matrix.
-  var product = matrixOfMinors.multiply(1 / originalDeterminant);
+  var product = matrixOfCoFactors.multiply(1 / originalDeterminant);
 
@@ -676,0 +702,0 @@ // Copy the data from the inverted temp matrix to this matrix

package.json

 {
   "name": "matrixmath",
-  "version": "2.2.0",
+  "version": "2.2.1",
   "author": "Johannes Koggdal <[e-mail]>",
@@ -5,0 +5,0 @@ "description": "Library for working with mathematical matrices.",

test/Matrix.js

@@ -847,3 +847,13 @@ var expect = require('expect.js');
 
-    it('should invert a square matrix', function() {
+    it('should invert a square 2x2 matrix', function() {
+      var matrix1 = new Matrix(2, 2).setData([0, -600, 240, 240]);
+      matrix1.invert();
+
+      expect(matrix1[0]).to.equal(1/600);
+      expect(matrix1[1]).to.equal(1/240);
+      expect(matrix1[2]).to.equal(-1/600);
+      expect(matrix1[3]).to.equal(0);
+    });
+
+    it('should invert a square 3x3 matrix', function() {
       var matrix1 = new Matrix(3, 3).setData([3, 0, 2, 2, 0, -2, 0, 1, 1]);
@@ -863,2 +873,24 @@ matrix1.invert();
 
+    it('should invert a square 4x4 matrix', function() {
+      var matrix1 = new Matrix(4, 4).setData([4, 0, 0, 0, 0, 0, 2, 0, 0, 1, 2, 0, 1, 0, 0, 1]);
+      matrix1.invert();
+
+      expect(matrix1[0]).to.equal(0.25);
+      expect(matrix1[1]).to.equal(0);
+      expect(matrix1[2]).to.equal(0);
+      expect(matrix1[3]).to.equal(0);
+      expect(matrix1[4]).to.equal(0);
+      expect(matrix1[5]).to.equal(-1);
+      expect(matrix1[6]).to.equal(1);
+      expect(matrix1[7]).to.equal(0);
+      expect(matrix1[8]).to.equal(0);
+      expect(matrix1[9]).to.equal(0.5);
+      expect(matrix1[10]).to.equal(0);
+      expect(matrix1[11]).to.equal(0);
+      expect(matrix1[12]).to.equal(-0.25);
+      expect(matrix1[13]).to.equal(0);
+      expect(matrix1[14]).to.equal(0);
+      expect(matrix1[15]).to.equal(1);
+    });
+
     it('should not invert a non-square matrix', function() {
@@ -865,0 +897,0 @@ var matrix1 = new Matrix(3, 2).setData([3, 0, 2, 0, 0, 1]);

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73725

increased by2.63%

Lines of code

1620

increased by3.18%

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