# @kaosat-dev/sylvester

0.0.21 • Public • Published

# sylvester

Modern and expanded implementation of James Coglan's "Sylvester" matrix math library. The original project can be found at http://sylvester.jcoglan.com/

# Documentation

The original documentation for "Sylvester" should help you through basic operations. An intro that contains node-specific features can also be found {on Chris Umbel's blog}[http://www.chrisumbel.com/article/sylvester_node_js_matrix_vector_math]. We're looking for someone to help get the documentation situation under control.

# Installation

``````npm install sylvester
``````

# Usage

## New Stuff

First I'd like to show some examples of features that aren't in the standard (non-node) Sylvester. I'll likely attempt to commit these back to Sylvester at some point soon.

Note that the decompositions are all available in pure JavaScript, but if the lapack NPM is installed with LAPACK built as a shared library then efficient native code will be used. The LAPACK integration is still highly experimental.

### Vector

``````require('sylvester');
var a = \$V([1, 2, 3]);
``````

element-wise log:

``````console.log(a.log());
``````

norm computation:

``````console.log(a.norm());
``````

element-wise multiplication:

``````a.elementMultiply(vector);
``````

element-wise division:

``````a.elementDivide(vector);
``````

remove first n nodes:

``````a.chomp(n);
``````

return vector with first n nodes:

``````a.top(n);
``````

add all elements into a single scalar:

``````a.sum()
``````

multiply all elements into a single scalar:

``````a.product()
``````

return a vector with the elements parameter on the bottom:

``````a.augment(elements)
``````

### Matrix

``````var A = \$M([[1, 2, 3], [4, 5, 6]]);
``````

return subset of rows, columns:

``````// startRow, endRow, startCol, endCol
A.slice(2, 3, 2, 3);
``````

divide matricies:

``````A.div(\$M([[0.5, 1], [1, 2], [2, 3]]));
``````

``````A.add(1);
A.subtract(1);
``````

element-wise log:

``````console.log(A.log());
``````

element-wise multiplication:

``````A.elementMultiply(vector)
``````

add all elements into a single scalar:

``````A.sum()
``````

returns a vector of the indexes of maximum values ([3 3]):

``````\$M([[1, 2, 3], [5, 4, 6]]).maxColumnIndexes()
``````

returns a vector of minimum column indexes ([1 2]):

``````\$M([[1, 2, 3], [5, 4, 6]]).minColumnIndexes();
``````

returns a vector of max values ([3 6]):

``````\$M([[1, 2, 3], [5, 4, 6]]).maxColumns()
``````

returns a vector of minimum values ([1 4]):

``````\$M([[1, 2, 3], [5, 4, 6]]).minColumns()
``````

create a 2x3 matrix of ones:

``````var Ones = Matrix.One(2, 3);
``````

LU decomposition (with partial pivoting)

var lu = A.lu(); console.log(lu.L); console.log(lu.U); console.log(lu.P);

QR decomposition (feature still inefficient and experimental, but uses pure javascript):

``````var qr = A.qr();
console.log(qr.Q);
console.log(qr.R);
``````

SVD decomposition (feature still inefficient and experimental, but uses pure javascript):

``````var svd = A.svd();
console.log(svd.U);
console.log(svd.S);
console.log(svd.V);
``````

PCA

``````var A = \$M([[1, 2], [5, 7]]).pcaProject(1).eql(\$M([
[-2.2120098720461616],
[-8.601913944732665]
]);
var pca = A.pcaProject(1);
var Z = pca.Z;
var A = Z.pcaRecover(pca.U);
``````

Solving systems of equations

``````// sovle Ax = b for x
var A = \$M([[2, 4], [2, 1]]);
var b = \$V([1, 0]);
console.log(A.solve(b));
``````

== Old Stuff

Below is a basic illustration of standard matrix/vector math using the standard Sylvester API. This documentation is rather incomplete and for further details please consult {the official sylvester API documentation}[http://sylvester.jcoglan.com/docs] at http://sylvester.jcoglan.com/docs.

### Vectors

``````require('sylvester');
``````

create two vectors:

``````var a = \$V([1, 2, 3]);
var b = \$V([2, 3, 4]);
``````

compute the dot product:

``````var r = a.dot(b);
``````

``````var c = a.add(b);
``````

multiply by scalar:

``````var d = a.x(2);
``````

### Matrices

``````require('sylvester');
``````

create two matrices:

``````var A = \$M([[1, 2], [3, 4]]);
var B = \$M([[1, 2, 3], [4, 5, 6]]);
``````

multiply the matrices:

``````var C = A.x(B);
``````

transpose a matrix:

``````var B_T = B.transpose();
// B is 2x3, B_T is 3x2
``````

## Package Sidebar

### Install

`npm i @kaosat-dev/sylvester`

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