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glogspace

Fill a strided array with logarithmically spaced values over a specified interval.

Installation

npm install @stdlib/blas-ext-base-glogspace

Alternatively,

• To load the package in a website via a script tag without installation and bundlers, use the ES Module available on the esm branch (see README).
• If you are using Deno, visit the deno branch (see README for usage intructions).
• For use in Observable, or in browser/node environments, use the Universal Module Definition (UMD) build available on the umd branch (see README).

The branches.md file summarizes the available branches and displays a diagram illustrating their relationships.

To view installation and usage instructions specific to each branch build, be sure to explicitly navigate to the respective README files on each branch, as linked to above.

Usage

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

glogspace( N, base, start, stop, endpoint, x, strideX )

Fills a strided array with logarithmically spaced values over a specified interval.

var x = [ 0.0, 0.0, 0.0, 0.0, 0.0, 0.0 ];

glogspace( x.length, 10.0, 0.0, 5.0, true, x, 1 );
// x => [ 1.0, 10.0, 100.0, 1000.0, 10000.0, 100000.0 ]

The function has the following parameters:

• N: number of indexed elements.
• base: base of the logarithmic scale.
• start: exponent of the starting value, where the starting value is given by base^start.
• stop: exponent of the final value, where the final value is given by base^stop.
• endpoint: boolean indicating whether to include the base^stop value when writing values to the input array. If true, the input array is filled with logarithmically spaced values over the closed interval [base^start, base^stop]. If false, the input array is filled with logarithmically spaced values over the half-open interval [base^start, base^stop).
• x: input array.
• strideX: stride length.

The N and stride parameters determine which elements in the strided array are accessed at runtime. For example, to fill every other element:

var x = [ 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0 ];

glogspace( 4, 10.0, 0.0, 3.0, true, x, 2 );
// x => [ 1.0, 0.0, 10.0, 0.0, 100.0, 0.0, 1000.0, 0.0 ]

Note that indexing is relative to the first index. To introduce an offset, use typed array views.

var Float64Array = require( '@stdlib/array-float64' );

// Initial array...
var x0 = new Float64Array( [ 0.0, 0.0, 0.0, 0.0, 0.0, 0.0 ] );

// Create an offset view...
var x1 = new Float64Array( x0.buffer, x0.BYTES_PER_ELEMENT*1 ); // start at 2nd element

// Fill every other element...
glogspace( 3, 10.0, 0.0, 2.0, true, x1, 2 );
// x0 => <Float64Array>[ 0.0, 1.0, 0.0, 10.0, 0.0, 100.0 ]

glogspace.ndarray( N, base, start, stop, endpoint, x, strideX, offsetX )

Fills a strided array with logarithmically spaced values over a specified interval using alternative indexing semantics.

var x = [ 0.0, 0.0, 0.0, 0.0, 0.0, 0.0 ];

glogspace.ndarray( x.length, 10.0, 0.0, 5.0, true, x, 1, 0 );
// x => [ 1.0, 10.0, 100.0, 1000.0, 10000.0, 100000.0 ]

The function has the following additional parameters:

• offsetX: starting index.

While typed array views mandate a view offset based on the underlying buffer, the offset parameter supports indexing semantics based on a starting index. For example, to access only the last three elements:

var x = [ 0.0, 0.0, 0.0, 0.0, 0.0, 0.0 ];

glogspace.ndarray( 3, 10.0, 0.0, 2.0, true, x, 1, x.length-3 );
// x => [ 0.0, 0.0, 0.0, 1.0, 10.0, 100.0 ]

Notes

• Let M be the number of generated values (which is either N or N+1 depending on whether endpoint is true or false, respectively). The spacing between the exponents is thus given by

  Δ = (stop-start)/(M-1)
  

  and the generated values are equal to base^(start+Δ*i) for i = 0, 1, ..., M-1.

• When the number of generated values is greater than 1 and endpoint is true, the set of values written to a provided input array is guaranteed to include the base^start and base^stop values. Beware, however, that values between base^start and base^stop are subject to floating-point rounding errors. Hence,

  var x = [ 0.0, 0.0, 0.0 ];
  
  glogspace( 3, 10.0, 0.0, 1.0, true, x, 1 );
  // x => [ 1.0, ~3.16, 10.0 ]

  where x[1] is only guaranteed to be approximately equal to the square root of 10.

• When N = 1 and endpoint is false, only the base^start value is written to a provided input array. When N = 1 and endpoint is true, only the base^stop value is written to a provided input array.

• If start < stop, the exponents are written to a provided input array in ascending order; otherwise, they are written in descending order.

• If N <= 0, both functions return x unchanged.

Examples

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

var x = discreteUniform( 10, -100, 100, {
    'dtype': 'generic'
});
console.log( x );

glogspace( x.length, 10.0, 0.0, 9.0, true, x, 1 );
console.log( x );

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Notice

This package is part of stdlib, a standard library for JavaScript and Node.js, with an emphasis on numerical and scientific computing. The library provides a collection of robust, high performance libraries for mathematics, statistics, streams, utilities, and more.

For more information on the project, filing bug reports and feature requests, and guidance on how to develop stdlib, see the main project repository.

Community

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License

See LICENSE.

Copyright

Copyright © 2016-2026. The Stdlib Authors.