Skip to content

README.md

Latest commit

 

History

History
173 lines (108 loc) · 4.99 KB

README.md

File metadata and controls

173 lines (108 loc) · 4.99 KB

gvander

Generate a Vandermonde matrix.

Usage

var gvander = require( '@stdlib/blas/ext/base/gvander' );

gvander( order, mode, M, N, x, strideX, out, ldo )

Generates a Vandermonde matrix.

var x = [ 1.0, 2.0, 3.0 ];
var out = [ 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0 ];

gvander( 'row-major', 1, 3, 3, x, 1, out, 3 );
// out => [ 1.0, 1.0, 1.0, 1.0, 2.0, 4.0, 1.0, 3.0, 9.0 ]

The function has the following parameters:

  • order: row-major (C-style) or column-major (Fortran-style) order.
  • mode: mode. If mode < 0, the function generates decreasing powers. If mode > 0, the function generates increasing powers.
  • M: number of rows in out and number of indexed elements in x.
  • N: number of columns in out.
  • x: input Array or typed array.
  • strideX: stride length for x.
  • out: output matrix.
  • ldo: stride of the first dimension of out (a.k.a., leading dimension of the matrix out).

gvander.ndarray( mode, M, N, x, strideX, offsetX, out, strideOut1, strideOut2, offsetOut )

Generates a Vandermonde matrix using alternative indexing semantics.

var x = [ 1.0, 2.0, 3.0 ];
var out = [ 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0 ];

gvander.ndarray( 1, 3, 3, x, 1, 0, out, 3, 1, 0 );
// out => [ 1.0, 1.0, 1.0, 1.0, 2.0, 4.0, 1.0, 3.0, 9.0 ]

The function has the following additional parameters:

  • offsetX: starting index for x.
  • strideOut1: stride length for the first dimension of out.
  • strideOut2: stride length for the second dimension of out.
  • offsetOut: starting index for out.

While typed array views mandate a view offset based on the underlying buffer, offset parameters support indexing semantics based on starting indices. For example, to use every other element from the input array starting from the second element:

var x = [ 0.0, 1.0, 0.0, 2.0, 0.0, 3.0 ];
var out = [ 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0 ];

gvander.ndarray( 1, 3, 3, x, 2, 1, out, 3, 1, 0 );
// out => [ 1.0, 1.0, 1.0, 1.0, 2.0, 4.0, 1.0, 3.0, 9.0 ]

Notes

  • If M <= 0 or N <= 0, both functions return out unchanged.
  • Both functions support array-like objects having getter and setter accessors for array element access (e.g., @stdlib/array/base/accessor).
  • Depending on the environment, the typed versions (dvander, svander, etc.) are likely to be significantly more performant.

Examples

var discreteUniform = require( '@stdlib/random/array/discrete-uniform' );
var zeros = require( '@stdlib/array/zeros' );
var gvander = require( '@stdlib/blas/ext/base/gvander' );

var M = 3;
var N = 4;

var x = discreteUniform( M, 0, 10, {
    'dtype': 'generic'
});
var out = zeros( M*N, 'generic' );
console.log( x );

gvander( 'row-major', -1, M, N, x, 1, out, N );
console.log( out );