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slogspace

Fill a single-precision floating-point strided array with logarithmically spaced values over a specified interval.

Installation

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

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

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

Fills a single-precision floating-point strided array with logarithmically spaced values over a specified interval.

var Float32Array = require( '@stdlib/array-float32' );

var x = new Float32Array( [ 0.0, 0.0, 0.0, 0.0, 0.0, 0.0 ] );

slogspace( x.length, 10.0, 0.0, 5.0, true, x, 1 );
// x => <Float32Array>[ 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 Float32Array.
• 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 Float32Array = require( '@stdlib/array-float32' );

var x = new Float32Array( [ 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0 ] );

slogspace( 4, 10.0, 0.0, 3.0, true, x, 2 );
// x => <Float32Array>[ 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 Float32Array = require( '@stdlib/array-float32' );

// Initial array...
var x0 = new Float32Array( [ 0.0, 0.0, 0.0, 0.0, 0.0, 0.0 ] );

// Create an offset view...
var x1 = new Float32Array( x0.buffer, x0.BYTES_PER_ELEMENT*1 ); // start at 2nd element

// Fill every other element...
slogspace( 3, 10.0, 0.0, 2.0, true, x1, 2 );
// x0 => <Float32Array>[ 0.0, 1.0, 0.0, 10.0, 0.0, 100.0 ]

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

Fills a single-precision floating-point strided array with logarithmically spaced values over a specified interval using alternative indexing semantics.

var Float32Array = require( '@stdlib/array-float32' );

var x = new Float32Array( [ 0.0, 0.0, 0.0, 0.0, 0.0, 0.0 ] );

slogspace.ndarray( x.length, 10.0, 0.0, 5.0, true, x, 1, 0 );
// x => <Float32Array>[ 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 Float32Array = require( '@stdlib/array-float32' );

var x = new Float32Array( [ 0.0, 0.0, 0.0, 0.0, 0.0, 0.0 ] );

slogspace.ndarray( 3, 10.0, 0.0, 2.0, true, x, 1, x.length-3 );
// x => <Float32Array>[ 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 Float32Array = require( '@stdlib/array-float32' );
  
  var x = new Float32Array( [ 0.0, 0.0, 0.0 ] );
  
  slogspace( 3, 10.0, 0.0, 1.0, true, x, 1 );
  // x => <Float32Array>[ 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 slogspace = require( '@stdlib/blas-ext-base-slogspace' );

var x = discreteUniform( 10, -100, 100, {
    'dtype': 'float32'
});
console.log( x );

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

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C APIs

Usage

#include "stdlib/blas/ext/base/slogspace.h"

stdlib_strided_slogspace( N, base, start, stop, endpoint, *X, strideX )

Fills a single-precision floating-point strided array with logarithmically spaced values over a specified interval.

#include <stdbool.h>

float x[] = { 0.0f, 0.0f, 0.0f, 0.0f };

stdlib_strided_slogspace( 4, 10.0f, 0.0f, 3.0f, true, x, 1 );

The function accepts the following arguments:

• N: [in] CBLAS_INT number of indexed elements.
• base: [in] float base of the logarithmic scale.
• start: [in] float exponent of the starting value.
• stop: [in] float exponent of the final value.
• endpoint: [in] bool 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: [out] float* input array.
• strideX: [in] CBLAS_INT stride length.

void stdlib_strided_slogspace( const CBLAS_INT N, const float base, const float start, const float stop, const bool endpoint, float *X, const CBLAS_INT strideX );

stdlib_strided_slogspace_ndarray( N, base, start, stop, endpoint, *X, strideX, offsetX )

Fills a single-precision floating-point strided array with logarithmically spaced values over a specified interval using alternative indexing semantics.

#include <stdbool.h>

float x[] = { 0.0f, 0.0f, 0.0f, 0.0f };

stdlib_strided_slogspace_ndarray( 4, 10.0f, 0.0f, 3.0f, true, x, 1, 0 );

The function accepts the following arguments:

• N: [in] CBLAS_INT number of indexed elements.
• base: [in] float base of the logarithmic scale.
• start: [in] float exponent of the starting value.
• stop: [in] float exponent of the final value.
• endpoint: [in] bool 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: [out] float* input array.
• strideX: [in] CBLAS_INT stride length.
• offsetX: [in] CBLAS_INT starting index.

void stdlib_strided_slogspace_ndarray( const CBLAS_INT N, const float base, const float start, const float stop, const bool endpoint, float *X, const CBLAS_INT strideX, const CBLAS_INT offsetX );

Examples

#include "stdlib/blas/ext/base/slogspace.h"
#include <stdio.h>
#include <stdbool.h>

int main( void ) {
    // Create a strided array:
    float x[] = { 0.0f, 0.0f, 0.0f, 0.0f, 0.0f, 0.0f, 0.0f, 0.0f };

    // Specify the number of indexed elements:
    const int N = 8;

    // Specify a stride:
    const int strideX = 1;

    // Fill the array:
    stdlib_strided_slogspace( N, 10.0f, 0.0f, 7.0f, true, x, strideX );

    // Print the result:
    for ( int i = 0; i < 8; i++ ) {
        printf( "x[ %i ] = %f\n", i, x[ i ] );
    }
}

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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.