mathjs/examples/matrices.js at develop · lineCode/mathjs · GitHub

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// matrices

// load math.js (using node.js)

const math = require('..')

// create matrices and arrays. a matrix is just a wrapper around an Array,

// providing some handy utilities.

console.log('create a matrix')

const a = math.matrix([1, 4, 9, 16, 25])

print(a) // [1, 4, 9, 16, 25]

const b = math.matrix(math.ones([2, 3]))

print(b) // [[1, 1, 1], [1, 1, 1]]

print(b.size()) // [2, 3]

// the Array data of a Matrix can be retrieved using valueOf()

const array = a.valueOf()

print(array) // [1, 4, 9, 16, 25]

// Matrices can be cloned

const clone = a.clone()

print(clone) // [1, 4, 9, 16, 25]

console.log()

// perform operations with matrices

console.log('perform operations')

print(math.sqrt(a)) // [1, 2, 3, 4, 5]

const c = [1, 2, 3, 4, 5]

print(math.factorial(c)) // [1, 2, 6, 24, 120]

console.log()

// create and manipulate matrices. Arrays and Matrices can be used mixed.

console.log('manipulate matrices')

const d = [[1, 2], [3, 4]]

print(d) // [[1, 2], [3, 4]]

const e = math.matrix([[5, 6], [1, 1]])

print(e) // [[5, 6], [1, 1]]

// set a submatrix.

// Matrix indexes are zero-based.

e.subset(math.index(1, [0, 1]), [[7, 8]])

print(e) // [[5, 6], [7, 8]]

const f = math.multiply(d, e)

print(f) // [[19, 22], [43, 50]]

const g = f.subset(math.index(1, 0))

print(g) // 43

console.log()

// get a sub matrix

// Matrix indexes are zero-based.

console.log('get a sub matrix')

const h = math.diag(math.range(1, 4))

print(h) // [[1, 0, 0], [0, 2, 0], [0, 0, 3]]

print(h.subset(math.index([1, 2], [1, 2]))) // [[2, 0], [0, 3]]

const i = math.range(1, 6)

print(i) // [1, 2, 3, 4, 5]

print(i.subset(math.index(math.range(1, 4)))) // [2, 3, 4]

console.log()

// resize a multi dimensional matrix

console.log('resizing a matrix')

const j = math.matrix()

let defaultValue = 0

j.resize([2, 2, 2], defaultValue)

print(j) // [[[0, 0], [0, 0]], [[0, 0], [0, 0]]]

print(j.size()) // [2, 2, 2]

j.resize([2, 2])

print(j) // [[0, 0], [0, 0]]

print(j.size()) // [2, 2]

console.log()

// setting a value outside the matrices range will resize the matrix.

// new elements will be initialized with zero.

console.log('set a value outside a matrices range')

const k = math.matrix()

k.subset(math.index(2), 6)

print(k) // [0, 0, 6]

console.log()

console.log('set a value outside a matrices range, setting other new entries to null')

const m = math.matrix()

defaultValue = null

m.subset(math.index(2), 6, defaultValue)

print(m) // [null, null, 6]

console.log()

// create ranges

console.log('create ranges')

print(math.range(1, 6)) // [1, 2, 3, 4, 5]

print(math.range(0, 18, 3)) // [0, 3, 6, 9, 12, 15]

print(math.range('2:-1:-3')) // [2, 1, 0, -1, -2]

print(math.factorial(math.range('1:6'))) // [1, 2, 6, 24, 120]

console.log()

/**

* Helper function to output a value in the console. Value will be formatted.

* @param {*} value

function print (value) {

const precision = 14

console.log(math.format(value, precision))

}

mathjs/examples/matrices.js at develop · lineCode/mathjs · GitHub

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