96 lines
3.0 KiB
Markdown
96 lines
3.0 KiB
Markdown
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---
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title: Matrix Calculator
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---
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## Matrix Calculator
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A Matrix Calculator is used to perform addition, subtraction or multiplication.
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Additionally it can perform operations specific to matrices, such as matrix transposition, inversion or define matrix's rank.
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Matrix is built from rows and columns (n x m). Operations done on matrices often put some restrictions on the matrix's dimensions.
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##### Addition:
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Addition is done by adding values of two matrices of **same** dimensions.
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The result is an array of same dimensions as the original ones.
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```javascript
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// matrices a and b are represented by an array of arrays (rows of columns)
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function addMatrices(a, b) {
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// we might want to add here constraints for the same dimensions
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if (!Array.isArray(a) || !Array.isArray(a[0]) || !Array.isArray(b) || !Array.isArray(b[0])) {
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throw new Error('a, b or it\'s children is not an array');
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}
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const result = [];
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for (let i = 0; i < a.length; i++) {
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result[i] = [];
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for (let j = 0; j < a[i].length; j++) {
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result[i][j] = a[i][j] + b[i][j];
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}
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}
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return result;
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}
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```
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##### Subtraction:
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Subtraction is done by subtracting values of two matrices of **same** dimensions.
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The result is an array of same dimensions as the original ones.
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```javascript
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// matrices a and b are represented by an array of arrays (rows of columns)
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function subtractMatrices(a, b) {
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// we might want to add here constraints for the same dimensions
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if (!Array.isArray(a) || !Array.isArray(a[0]) || !Array.isArray(b) || !Array.isArray(b[0])) {
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throw new Error('a, b or it\'s children is not an array');
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}
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const result = [];
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for (let i = 0; i < a.length; i++) {
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result[i] = [];
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for (let j = 0; j < a[i].length; j++) {
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result[i][j] = a[i][j] - b[i][j];
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}
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}
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return result;
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}
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```
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##### Multiplication:
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Multiplication can be done either by multiplying a matrix by a scalar, or by multiplying matrices.
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If we multiply two matrices, it can only be done if the number of columns in the left matrix is equal to number of rows in the right matrix.
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```javascript
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// matrices a and b are represented by an array of arrays (rows of columns)
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function multiplyMatrices(a, b) {
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// we might want to add here constraints for the dimensions
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//let's assume that b has to be either a scalar or an array
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if (!Array.isArray(a) || !Array.isArray(a[0]) || ((!Array.isArray(b) || !Array.isArray(b[0])) && isNaN(b))) {
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throw new Error('a, b or it\'s children is not an array');
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}
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if (!isNaN(b)) {
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for (let i = 0; i < a.length; i++) {
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for (let j = 0; j < a[i].length; j++) {
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a[i][j] = a[i][j] * b;
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}
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}
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return a;
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}
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const result = [];
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for (let i = 0; i < a.length; i++) {
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result[i] = [];
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for (let j = 0; j < a[i].length; j++) {
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let sum = 0;
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for (let k = 0; k < b[i].length; k++) {
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sum += a[i][k] * b[k][j];
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}
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result[i][j] = sum;
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}
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}
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return result;
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}
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```
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#### More information:
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https://en.wikipedia.org/wiki/Matrix_(mathematics)
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