finishing touches on matrixMult.js

Author: plooney81

Maths/matrixMult.js

@@ -1,87 +1,87 @@
 
 // MatrixCheck tests to see if all of the rows of the matrix inputted have similar size columns
-const matrixCheck = (matrix)=>{
- let columnNumb;
- for (let index = 0; index < matrix.length; index++){
- if (index == 0){
- columnNumb = matrix[index].length;
- } else if (matrix[index].length != columnNumb){
+const matrixCheck = (matrix) => {
+ let columnNumb
+ for (let index = 0; index < matrix.length; index++) {
+ if (index === 0) {
+ columnNumb = matrix[index].length
+ } else if (matrix[index].length !== columnNumb) {
  console.log('The columns in this array are not equal')
  } else {
- return columnNumb;
+ return columnNumb
  }
  }
 }
 
 // tests to see if the matrices have a like side, i.e. the row length on the first matrix matches the column length on the second matrix, or vise versa.
-const twoMatricesCheck = (first, second)=>{
- const [firstRowLength, secondRowLength, firstColLength, secondColLength] = [first.length, second.length, matrixCheck(first), matrixCheck(second)];
-  if (firstRowLength != secondColLength || secondRowLength != firstColLength){
-  console.log('These matrices do not have a common side');
-  return false;
-  } else {
-  return true;
-  }
+const twoMatricesCheck = (first, second) => {
+ const [firstRowLength, secondRowLength, firstColLength, secondColLength] = [first.length, second.length, matrixCheck(first), matrixCheck(second)]
+ if (firstRowLength !== secondColLength || secondRowLength !== firstColLength) {
+ console.log('These matrices do not have a common side')
+ return false
+ } else {
+ return true
+ }
 }
 
 // returns an empty array that has the same number of rows as the left matrix being multiplied.
- //Uses Array.prototype.map() to loop over the first (or left) matrix and returns an empty array on each iteration.
-const initiateEmptyArray = (first, second)=>{
- if (twoMatricesCheck(first, second)){
- const emptyArray = first.map(()=>{
- return [''];
+// Uses Array.prototype.map() to loop over the first (or left) matrix and returns an empty array on each iteration.
+const initiateEmptyArray = (first, second) => {
+ if (twoMatricesCheck(first, second)) {
+ const emptyArray = first.map(() => {
+ return ['']
  })
- return emptyArray;
- }else{
- return false;
+ return emptyArray
+ } else {
+ return false
  }
 }
 
 // Finally, `matrixMult` uses `Array.prototype.push()`, multiple layers of nested `for` loops, the addition assignment `+=` operator and multiplication operator `*` to perform the dot product between two matrices of differing sizes.
- // Dot product, takes the row of the first matrix and multiplies it by the column of the second matrix, the `twoMatricesCheck` tested to see if they were the same size already.
- // The dot product for each iteration is then saved to its respective index into `multMatrix`.
-const matrixMult = (firstArray, secondArray)=>{
- let multMatrix = initiateEmptyArray(firstArray, secondArray);
- for (let rm = 0; rm < firstArray.length; rm++){
- rowMult = [];
- for (let col = 0; col < firstArray[0].length; col++){
- rowMult.push(firstArray[rm][col]);
+// Dot product, takes the row of the first matrix and multiplies it by the column of the second matrix, the `twoMatricesCheck` tested to see if they were the same size already.
+// The dot product for each iteration is then saved to its respective index into `multMatrix`.
+const matrixMult = (firstArray, secondArray) => {
+ const multMatrix = initiateEmptyArray(firstArray, secondArray)
+ for (let rm = 0; rm < firstArray.length; rm++) {
+ const rowMult = []
+ for (let col = 0; col < firstArray[0].length; col++) {
+ rowMult.push(firstArray[rm][col])
  }
- for (let cm = 0; cm < firstArray.length; cm++){
- colMult = [];
- for (let row = 0; row < secondArray.length; row++){
- colMult.push(secondArray[row][cm]);
+ for (let cm = 0; cm < firstArray.length; cm++) {
+ const colMult = []
+ for (let row = 0; row < secondArray.length; row++) {
+ colMult.push(secondArray[row][cm])
  }
- let newNumb = 0;
- for (let index = 0; index < rowMult.length; index++){
- newNumb += rowMult[index] * colMult[index];
+ let newNumb = 0
+ for (let index = 0; index < rowMult.length; index++) {
+ newNumb += rowMult[index] * colMult[index]
  }
- multMatrix[rm][cm] = newNumb;
+ multMatrix[rm][cm] = newNumb
  }
  }
- return multMatrix;
+ return multMatrix
 }
 
 const firstMatrix = [
  [1, 2],
  [3, 4]
-];
+]
 
 const secondMatrix = [
  [5, 6],
  [7, 8]
-];
+]
 
-console.log(matrixMult(firstMatrix, secondMatrix)); // [ [ 19, 22 ], [ 43, 50 ] ]
+console.log(matrixMult(firstMatrix, secondMatrix)) // [ [ 19, 22 ], [ 43, 50 ] ]
 
 const thirdMatrix = [
  [-1, 4, 1],
- [7, -6, 2],
-];
+ [7, -6, 2]
+]
 const fourthMatrix = [
  [2, -2],
  [5, 3],
- [3, 2],
-];
+ [3, 2]
+]
 
-console.log(matrixMult(thirdMatrix, fourthMatrix)); // [ [ 21, 16 ], [ -10, -28 ] ]
+console.log(matrixMult(thirdMatrix, fourthMatrix)) // [ [ 21, 16 ], [ -10, -28 ] ]