npm package: @stdlib/blas-ext-base-dlinspace
Description: Fill a double-precision floating-point strided array with linearly spaced values over a specified interval.
Author: The Stdlib Authors
Latest version: 0.1.1

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# dlinspace

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> Fill a double-precision floating-point strided array with linearly spaced values over a specified interval.

<section class="installation">

## Installation

```bash
npm install @stdlib/blas-ext-base-dlinspace
```

</section>

<section class="usage">

## Usage

```javascript
var dlinspace = require( '@stdlib/blas-ext-base-dlinspace' );
```

#### dlinspace( N, start, stop, endpoint, x, strideX )

Fills a double-precision floating-point strided array with linearly spaced values over a specified interval.

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

var x = new Float64Array( [ 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0 ] );

dlinspace( x.length, 0.0, 7.0, true, x, 1 );
// x => <Float64Array>[ 0.0, 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0 ]
```

The function has the following parameters:

-   **N**: number of indexed elements.
-   **start**: start of interval.
-   **stop**: end of interval.
-   **endpoint**: boolean indicating whether to include the `stop` value when writing values to the input array. If `true`, the input array is filled with evenly spaced values over the closed interval `[start, stop]`. If `false`, the input array is filled with evenly spaced values over the half-open interval `[start, stop)`.
-   **x**: input [`Float64Array`][@stdlib/array/float64].
-   **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:

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

var x = new Float64Array( [ 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0 ] );

dlinspace( 4, 1.0, 5.0, false, x, 2 );
// x => <Float64Array>[ 1.0, 0.0, 2.0, 0.0, 3.0, 0.0, 4.0, 0.0 ]
```

Note that indexing is relative to the first index. To introduce an offset, use [`typed array`][mdn-typed-array] views.

```javascript
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...
dlinspace( 3, 1.0, 3.0, true, x1, 2 );
// x0 => <Float64Array>[ 0.0, 1.0, 0.0, 2.0, 0.0, 3.0 ]
```

#### dlinspace.ndarray( N, start, stop, endpoint, x, strideX, offsetX )

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

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

var x = new Float64Array( [ 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0 ] );

dlinspace.ndarray( x.length, 0.0, 7.0, true, x, 1, 0 );
// x => <Float64Array>[ 0.0, 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0 ]
```

The function has the following additional parameters:

-   **offsetX**: starting index.

While [`typed array`][mdn-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:

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

var x = new Float64Array( [ 0.0, 0.0, 0.0, 0.0, 0.0, 0.0 ] );

dlinspace.ndarray( 3, 1.0, 3.0, true, x, 1, x.length-3 );
// x => <Float64Array>[ 0.0, 0.0, 0.0, 1.0, 2.0, 3.0 ]
```

</section>

<!-- /.usage -->

<section class="notes">

## 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 values is thus given by

    ```text
    Δ = (stop-start)/(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 `start` and `stop` values. Beware, however, that values between `start` and `stop` are subject to floating-point rounding errors. Hence,

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

    var x = new Float64Array( [ 0.0, 0.0, 0.0 ] );

    dlinspace( 3, 0.0, 1.0, true, x, 1 );
    // x => <Float64Array>[ 0.0, ~0.5, 1.0 ]
    ```

    where `x[1]` is only guaranteed to be approximately equal to `0.5`.

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

-   If `start < stop`, values are written to a provided input array in ascending order; otherwise, values are written in descending order.

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

</section>

<!-- /.notes -->

<section class="examples">

## Examples

<!-- eslint no-undef: "error" -->

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

var x = discreteUniform( 10, -100, 100, {
    'dtype': 'float64'
});
console.log( x );

dlinspace( x.length, 0.0, 10.0, true, x, 1 );
console.log( x );
```

</section>

<!-- /.examples -->

<!-- C interface documentation. -->

* * *

<section class="c">

## C APIs

<!-- Section to include introductory text. Make sure to keep an empty line after the intro `section` element and another before the `/section` close. -->

<section class="intro">

</section>

<!-- /.intro -->

<!-- C usage documentation. -->

<section class="usage">

### Usage

```c
#include "stdlib/blas/ext/base/dlinspace.h"
```

#### stdlib_strided_dlinspace( N, start, stop, endpoint, \*X, strideX )

Fills a double-precision floating-point strided array with linearly spaced values over a specified interval.

```c
#include <stdbool.h>

double x[] = { 0.0, 0.0, 0.0, 0.0 };

stdlib_strided_dlinspace( 4, 1.0, 5.0, true, x, 1 );
```

The function accepts the following arguments:

-   **N**: `[in] CBLAS_INT` number of indexed elements.
-   **start**: `[in] double` start of interval.
-   **stop**: `[in] double` end of interval.
-   **endpoint**: `[in] bool` boolean indicating whether to include the `stop` value when writing values to the input array. If `true`, the input array is filled with evenly spaced values over the closed interval `[start, stop]`. If `false`, the input array is filled with evenly spaced values over the half-open interval `[start, stop)`.
-   **X**: `[out] double*` input array.
-   **strideX**: `[in] CBLAS_INT` stride length.

```c
void stdlib_strided_dlinspace( const CBLAS_INT N, const double start, const double stop, const bool endpoint, double *X, const CBLAS_INT strideX );
```

<!-- lint disable maximum-heading-length -->

#### stdlib_strided_dlinspace_ndarray( N, start, stop, endpoint, \*X, strideX, offsetX )

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

```c
#include <stdbool.h>

double x[] = { 0.0, 0.0, 0.0, 0.0 };

stdlib_strided_dlinspace_ndarray( 4, 1.0, 5.0, true, x, 1, 0 );
```

The function accepts the following arguments:

-   **N**: `[in] CBLAS_INT` number of indexed elements.
-   **start**: `[in] double` start of interval.
-   **stop**: `[in] double` end of interval.
-   **endpoint**: `[in] bool` boolean indicating whether to include the `stop` value when writing values to the input array. If `true`, the input array is filled with evenly spaced values over the closed interval `[start, stop]`. If `false`, the input array is filled with evenly spaced values over the half-open interval `[start, stop)`.
-   **X**: `[out] double*` input array.
-   **strideX**: `[in] CBLAS_INT` stride length.
-   **offsetX**: `[in] CBLAS_INT` starting index.

```c
void stdlib_strided_dlinspace_ndarray( const CBLAS_INT N, const double start, const double stop, const bool endpoint, double *X, const CBLAS_INT strideX, const CBLAS_INT offsetX );
```

</section>

<!-- /.usage -->

<!-- C API usage notes. Make sure to keep an empty line after the `section` element and another before the `/section` close. -->

<section class="notes">

</section>

<!-- /.notes -->

<!-- C API usage examples. -->

<section class="examples">

### Examples

```c
#include "stdlib/blas/ext/base/dlinspace.h"
#include <stdio.h>
#include <stdbool.h>

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

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

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

    // Fill the array:
    stdlib_strided_dlinspace( N, 0.0, 10.0, true, x, strideX );

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

</section>

<!-- /.examples -->

</section>

<!-- /.c -->

<!-- Section for related `stdlib` packages. Do not manually edit this section, as it is automatically populated. -->

<section class="related">

</section>

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<section class="main-repo" >

* * *

## Notice

This package is part of [stdlib][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][stdlib], see the main project [repository][stdlib].

#### Community

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---

## License

See [LICENSE][stdlib-license].


## Copyright

Copyright &copy; 2016-2026. The Stdlib [Authors][stdlib-authors].

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