class static

la.Matrix

Source: ladoc.js:115

Represents a dense matrix (2d array), wraps a C++ object implemented in glib/base/ds.h.

Properties

cols
rows

Methods

at(rowIdx, colIdx)
colMaxIdx(colIdx)
colNorms()
diag()
frob()
getCol(colIdx)
getColSubmatrix(intVec)
getRow(rowIdx)
getSubmatrix(minRow, maxRow, minCol, maxCol)
load(fin)
minus(mat)
multiply(arg)
multiplyT(arg)
normalizeCols()
plus(mat)
print()
put(rowIdx, colIdx, arg)
rowMaxIdx(rowIdx)
rowNorms()
save(fout)
setCol(colIdx, vec)
setRow(rowIdx, vec)
solve(vec)
sparse()
toArray()
toMat()
toString()
transpose()

new Matrix([arg])

Matrix class.

Example 

// import la module
var la = require('qminer').la;
// create new matrix with matrixArg
var mat = new la.Matrix({"rows": 3, "cols": 2, "random": true}); // creates a 3 x 2 matrix with random values
// create a new matrix with nested arrays
var mat2 = new la.Matrix([[1, 7, 4], [-10, 0, 3]]); // creates a 2 x 3 matrix with the designated values

Parameter

Name Type Optional Description

arg

(module:la~matrixArg, Array of Array of number, or module:la.Matrix)

Yes

Constructor arguments. There are three ways of constructing:
1. Using the parameter object module:la~matrixArg,
2. using a nested array of matrix elements (row major). Example: [[1,2],[3,4]] has two rows, the first row is [1,2],
3. using a dense matrix (copy constructor).

Properties

cols

Gives the number of columns of matrix. Type number.

Example 

// import la module
var la = require('qminer').la;
// create the matrix
var mat = new la.Matrix([[1, 2], [3, 1], [-4, 5]]);
// get the number of cols
var colsN = mat.cols; // returns 2

rows

Gives the number of rows of matrix. Type number.

Example 

// import la module
var la = require('qminer').la;
// create the matrix
var mat = new la.Matrix([[1, 2], [3, 1], [-4, 5]]);
// get the number of rows
var rowN = mat.rows; // returns 3

Methods

at(rowIdx, colIdx) → number

Returns an element of matrix.

Example 

// import la module
var la = require('qminer').la;
// create a new matrix
var mat = new la.Matrix([[2, 3], [-2, -2], [-3, 1]]);
// get the value at the index (2, 1)
var value = mat.at(2, 1); // returns the value 1

Parameters

Name Type Optional Description

rowIdx

number

 

Row index (zero based).

colIdx

number

 

Column index (zero based).
Returns

numberB The matrix element.

colMaxIdx(colIdx) → number

Gives the index of the maximum element in the given column.

Example 

// import la module
var la = require('qminer').la;
// create the matrix
var mat = new la.Matrix([[1, 2], [3, 1], [-4, 5]]);
// get the row id of the maximum value of the second column
var maxRow = mat.colMaxIdx(1); // returns the value 2

Parameter

Name Type Optional Description

colIdx

number

 

Column index (zero based).
Returns

numberB Row index (zero based) of the maximum value in colIdx-th column of matrix.

colNorms() → module:la.Vector

Calculates the matrix column norms.

Example 

// import la module
var la = require('qminer').la;
// create a new matrix
var mat = new la.Matrix([[3, 4], [4, 15/2]]);
// get the row norms of the matrix
var rowNorms = mat.colNorms(); // returns the vector [5, 17/2]
Returns

module:la.VectorB Vector, where the value at i-th index is the norm of the i-th column of matrix.

diag() → module:la.Vector

Returns the diagonal elements of matrix.

Example 

// import la module
var la = require('qminer').la;
// create a new matrix
var mat = new la.Matrix([[1, -1, 0], [15, 8, 3], [0, 1, 0]]);
// call diag function
var vec = mat.diag(); // returns a vector [1, 8, 0]
Returns

module:la.VectorB Vector containing the diagonal elements.

frob() → number

Returns the frobenious norm of matrix.

Example 

// import la module
var la = require('qminer').la;
// create the matrix
var mat = new la.Matrix([[1, 2], [3, 4]]);
// get the frobenious norm of the matrix
var frob = mat.frob(); // returns the value Math.sqrt(30)
Returns

numberB Frobenious norm of matrix.

getCol(colIdx) → module:la.Vector

Returns the corresponding column of matrix as vector.

Example 

// import la module
var la = require('qminer').la;
// create the matrix
var mat = new la.Matrix([[1, 2], [3, 1], [-4, 5]]);
// get the second column of the matrix
var col = mat.getCol(1);

Parameter

Name Type Optional Description

colIdx

number

 

Column index (zero based).
Returns

module:la.VectorB The colIdx-th column of matrix.

getColSubmatrix(intVec) → module:la.Matrix

Gets the submatrix from the column ids.

Example 

//import la module
var la = require('qminer').la;
// create a random matrix
var mat = new la.Matrix({ rows: 10, cols: 10, random: true });
// get the submatrix containing the 1, 2 and 4 column
var submat = mat.getColSubmatrix(new la.IntVector([0, 1, 3]));

Parameter

Name Type Optional Description

intVec

module:la.IntVector

 

The vector containing the column ids.
Returns

module:la.MatrixB The submatrix containing the the columns of the original matrix.

getRow(rowIdx) → module:la.Vector

Returns the corresponding row of matrix as vector.

Example 

// import la module
var la = require('qminer').la;
// create the matrix
var mat = new la.Matrix([[1, 2], [3, 1], [-4, 5]]);
// get the first row of the matrix
var row = mat.getRow(1);

Parameter

Name Type Optional Description

rowIdx

number

 

Row index (zero based).
Returns

module:la.VectorB The rowIdx-th row of matrix.

getSubmatrix(minRow, maxRow, minCol, maxCol) → module:la.Matrix

Gets the submatrix from the column ids.

Example 

//import la module
var la = require('qminer').la;
// create a random matrix
var mat = new la.Matrix({ rows: 10, cols: 10, random: true });
// get the submatrix containing from the position (1, 2) to (7, 4)
var submat = mat.getSubmatrix(1, 7, 2, 4);

Parameters

Name Type Optional Description

minRow

number

 

The minimum row index.

maxRow

number

 

The maximum row index.

minCol

number

 

The minimum column index.

maxCol

number

 

The maximum column index.
Returns

module:la.MatrixB The submatrix of the original matrix.

load(fin) → module:la.Matrix

Loads the matrix from input stream.

Example 

// import the modules
var fs = require('qminer').fs;
var la = require('qminer').la;
// create an empty matrix
var mat = new la.Matrix();
// open a read stream ('mat.dat' is pre-saved)
var fin = fs.openRead('mat.dat');
// load the matrix
mat.load(fin);

Parameter

Name Type Optional Description

fin

module:fs.FIn

 

Input stream.
Returns

module:la.MatrixB Self. It is made out of the input stream fin.

minus(mat) → module:la.Matrix

Substracts two matrices.

Example 

// import la module
var la = require('qminer').la;
// create two matrices
var mat = new la.Matrix([[1, 2], [-1, 5]]);
var mat2 = new la.Matrix([[1, -1], [3, 2]]);
// substract the matrices
// the return matrix is
//  0   3
// -4   3
var diff = mat.minus(mat2);

Parameter

Name Type Optional Description

mat

module:la.Matrix

 

The second matrix.
Returns

module:la.MatrixB The difference of the matrices.

multiply(arg) → (module:la.Matrix or module:la.Vector)

Right-hand side multiplication of matrix with parameter.

Example 

// import la module
var la = require('qminer').la;
// create a new matrix
var mat = new la.Matrix([[1, 2], [-1, 5]]);
// create a new vector
var vec = new la.Vector([1, -1]);
//multiply mat and vec
var vec2 = mat.multiply(vec); // returns vector [-1, -6]

Parameter

Name Type Optional Description

arg

(number, module:la.Vector, module:la.SparseVector, module:la.Matrix, or module:la.SparseMatrix)

 

Multiplication input. Supports scalar, vector and matrix input.
Returns

(module:la.Matrix or module:la.Vector)B
1. module:la.Matrix, if arg is a number, module:la.Matrix or module:la.SparseMatrix.
2. module:la.Vector, if arg is a module:la.Vector or module:la.SparseVector.

multiplyT(arg) → (module:la.Matrix or module:la.Vector)

Matrix transpose and right-hand side multiplication of matrix with parameter.

Example 

// import la module
var la = require('qminer').la;
// create a new matrix
var mat = new la.Matrix([[1, 2], [-1, 5]]);
// create a new vector
var vec = new la.Vector([1, -1]);
//multiply mat and vec
var vec2 = mat.multiplyT(vec); // returns vector [2, -3]

Parameter

Name Type Optional Description

arg

(number, module:la.Vector, module:la.SparseVector, module:la.Matrix, or module:la.SparseMatrix)

 

Multiplication input. Supports scalar, vector and matrix input.
Returns

(module:la.Matrix or module:la.Vector)B
1. module:la.Matrix, if arg is a number, module:la.Matrix or a module:la.SparseMatrix.
2. module:la.Vector, if arg is a module:la.Vector or a module:la.SparseVector.

normalizeCols() → module:la.Matrix

Normalizes each column of matrix.

Example 

// import la module
var la = require('qminer').la;
// create a new matrix
var mat = new la.Matrix([[3, 4], [4, 15/2]]);
// normalize the columns of the matrix
// the matrix is going to be of the form:
// 3/5     8/17
// 4/5    15/17
mat.normalizeCols();
Returns

module:la.MatrixB Self. The columns of matrix are normalized.

plus(mat) → module:la.Matrix

Adds two matrices.

Example 

// import la module
var la = require('qminer').la;
// create two matrices
var mat = new la.Matrix([[1, 2], [-1, 5]]);
var mat2 = new la.Matrix([[1, -1], [3, 2]]);
// add the matrices
// the return matrix is
// 2   1
// 2   7
var sum = mat.plus(mat2);

Parameter

Name Type Optional Description

mat

module:la.Matrix

 

The second matrix.
Returns

module:la.MatrixB The sum of the matrices.

print()

Prints the matrix on-screen.

Example 

// import la module
var la = require('qminer').la;
// create a new matrix
var mat = new la.Matrix([[1, 2], [3, 4]]);
// print the matrix
// each row represents a row in the matrix. For this example:
// 1  2
// 3  4
mat.print();

put(rowIdx, colIdx, arg) → module:la.Matrix

Sets an element or a block of matrix.

Example 

// import la module
var la = require('qminer').la;
// create a new matrix
var mat = new la.Matrix([[1, 2, 3], [4, 5, 6], [7, 8, 9]]);
var arg = new la.Matrix([[10, 11], [12, 13]]);
mat.put(0, 1, arg);
// updates the matrix to
// 1  10  11
// 4  12  13
// 7   8   9

Parameters

Name Type Optional Description

rowIdx

number

 

Row index (zero based).

colIdx

number

 

Column index (zero based).

arg

(number or module:la.Matrix)

 

A number or a matrix. If arg is of type module:la.Matrix, it gets copied, where the argument's upper left corner, arg.at(0,0), gets copied to position (rowIdx, colIdx).
Returns

module:la.MatrixB Self. The (rowIdx, colIdx) value/block is changed.

rowMaxIdx(rowIdx) → number

Gives the index of the maximum element in the given row.

Example 

// import la module
var la = require('qminer').la;
// create the matrix
var mat = new la.Matrix([[1, 2], [3, 1], [-4, 5]]);
// get the column id of the maximum value of the second row
var maxRow = mat.rowMaxIdx(1); // returns the value 0

Parameter

Name Type Optional Description

rowIdx

number

 

Row index (zero based).
Returns

numberB Column index (zero based) of the maximum value in the rowIdx-th row of matrix.

rowNorms() → module:la.Vector

Calculates the matrix row norms.

Example 

// import la module
var la = require('qminer').la;
// create a new matrix
var mat = new la.Matrix([[3, 4], [4, 15/2]]);
// get the row norms of the matrix
var rowNorms = mat.rowNorms(); // returns the vector [5, 17/2]
Returns

module:la.VectorB Vector, where the value at i-th index is the norm of the i-th row of matrix.

save(fout) → module:fs.FOut

Saves the matrix as output stream.

Example 

// import the modules
var fs = require('qminer').fs;
var la = require('qminer').la;
// create new matrix
var mat = new la.Matrix([[1, 2], [3, 4]]);
// open write stream
var fout = fs.openWrite('mat.dat');
// save matrix and close write stream
mat.save(fout).close();

Parameter

Name Type Optional Description

fout

module:fs.FOut

 

Output stream.
Returns

module:fs.FOutB The output stream fout.

setCol(colIdx, vec) → module:la.Matrix

Sets the column of the matrix.

Example 

// import la module
var la = require('qminer').la;
// create a matrix
var mat = new la.Matrix([[1, -3, 2], [9, 2, -4],  [-2, 3, 3]]);
// create a vector
var vec = new la.Vector([-3, 2, 2]);
// set the first column of the matrix with the vector
// the changed matrix is now
// -3   -3    2
//  2    2   -4
//  2    3    3
mat.setCol(0, vec);

Parameters

Name Type Optional Description

colIdx

number

 

Column index (zero based).

vec

module:la.Vector

 

The new column of matrix.
Returns

module:la.MatrixB Self. The colIdx-th column is changed.

setRow(rowIdx, vec) → module:la.Matrix

Sets the row of matrix.

Example 

// import la module
var la = require('qminer').la;
// create a matrix
var mat = new la.Matrix([[1, -3, 2], [9, 2, -4],  [-2, 3, 3]]);
// create a vector
var vec = new la.Vector([-3, 2, 2]);
// set the first row of the matrix with the vector
// the changed matrix is now
// -3    2    2
//  9    2   -4
// -2    3    3
mat.setRow(0, vec);

Parameters

Name Type Optional Description

rowIdx

number

 

Row index (zero based).

vec

module:la.Vector

 

The new row of matrix.
Returns

module:la.MatrixB Self. The rowIdx-th row is changed.

solve(vec) → module:la.Vector

Solves the linear system.

Example 

// import la module
var la = require('qminer').la;
// create a new matrix
var M = new la.Matrix([[1, 2], [-1, -5]]);
// create a new vector
var b = new la.Vector([-1, -6]);
// solve the linear system M*x = b
var x = M.solve(b); // returns vector [1, -1]

Parameter

Name Type Optional Description

vec

module:la.Vector

 

The right-hand side of the equation.
Returns

module:la.VectorB The solution of the linear system.

sparse() → module:la.SparseMatrix

Transforms the matrix from dense to sparse format.

Example 

// import la module
var la = require('qminer').la;
// create the matrix
var mat = new la.Matrix([[1, 2], [0, 3], [-4, 0]]);
// transform the matrix into the sparse form
var spMat = mat.sparse();
Returns

module:la.SparseMatrixB Sparse column matrix representation of dense matrix.

toArray() → Array of Array of number

Copies the matrix into a JavaScript array of arrays of numbers.

Example 

// import la module
var la = require('qminer').la;
// create a new matrix
var mat = new la.Matrix([[1, 2], [3, 4]]);
// create a JavaScript array out of matrix
var arr = mat.toArray(); // returns an array [[1, 2], [3, 4]]
Returns

Array of Array of numberB A JavaScript array of arrays of numbers.

toMat() → module:la.Matrix

Returns a copy of the matrix.

Example 

// import la module
var la = require('qminer').la;
// create a random matrix
var mat = new la.Matrix({ rows: 5, cols: 4, random: true });
// create a copy of the matrix
var copy = mat.toMat();
Returns

module:la.MatrixB Matrix copy.

toString() → string

Returns the matrix as string.

Example 

// import la module
var la = require('qminer').la;
// create a new matrix
var mat = new la.Matrix([[1, 2], [3, 5]]);
// get matrix as string
var text = mat.toString(); // returns `1 2 \n3 5 \n\n`
Returns

stringB Dense matrix as string.

transpose() → module:la.Matrix

Transposes the matrix.

Example 

// import la module
var la = require('qminer').la;
// create a matrix
var mat = new la.Matrix([[2, -5], [3, 1]]);
// transpose the matrix
// the return matrix is
//  2   3
// -5   1
var trans = mat.transpose();
Returns

module:la.MatrixB Transposed matrix.