npm package: @stdlib/blas-ext-base-ndarray-dindex-of
Description: Return the first index of a specified search element in a one-dimensional double-precision floating-point ndarray.
Author: The Stdlib Authors
Latest version: 0.1.1

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# dindexOf

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> Return the first index of a search element in a one-dimensional double-precision floating-point ndarray.

<section class="intro">

</section>

<!-- /.intro -->

<section class="installation">

## Installation

```bash
npm install @stdlib/blas-ext-base-ndarray-dindex-of
```

</section>

<section class="usage">

## Usage

```javascript
var dindexOf = require( '@stdlib/blas-ext-base-ndarray-dindex-of' );
```

#### dindexOf( arrays )

Returns the first index of a specified search element in a one-dimensional double-precision floating-point ndarray.

```javascript
var Float64Array = require( '@stdlib/array-float64' );
var scalar2ndarray = require( '@stdlib/ndarray-from-scalar' );
var ndarray = require( '@stdlib/ndarray-base-ctor' );

var xbuf = new Float64Array( [ 1.0, 3.0, 4.0, 2.0 ] );
var x = new ndarray( 'float64', xbuf, [ 4 ], [ 1 ], 0, 'row-major' );

var searchElement = scalar2ndarray( 2.0, {
    'dtype': 'float64'
});

var fromIndex = scalar2ndarray( 0, {
    'dtype': 'generic'
});

var idx = dindexOf( [ x, searchElement, fromIndex ] );
// returns 3
```

The function has the following parameters:

-   **arrays**: array-like object containing the following ndarrays:

    -   a one-dimensional input ndarray.
    -   a zero-dimensional ndarray containing the search element.
    -   a zero-dimensional ndarray containing the index from which to begin searching.

If the function is unable to find a search element, the function returns `-1`.

```javascript
var Float64Array = require( '@stdlib/array-float64' );
var scalar2ndarray = require( '@stdlib/ndarray-from-scalar' );
var ndarray = require( '@stdlib/ndarray-base-ctor' );

var xbuf = new Float64Array( [ 1.0, 3.0, 4.0, 2.0 ] );
var x = new ndarray( 'float64', xbuf, [ 4 ], [ 1 ], 0, 'row-major' );

var searchElement = scalar2ndarray( 10.0, {
    'dtype': 'float64'
});

var fromIndex = scalar2ndarray( 0, {
    'dtype': 'generic'
});

var idx = dindexOf( [ x, searchElement, fromIndex ] );
// returns -1
```

</section>

<!-- /.usage -->

<section class="notes">

## Notes

-   If a specified starting search index is negative, the function resolves the starting search index by counting backward from the last element (where `-1` refers to the last element).

</section>

<!-- /.notes -->

<section class="examples">

## Examples

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

```javascript
var discreteUniform = require( '@stdlib/random-array-discrete-uniform' );
var ndarray = require( '@stdlib/ndarray-base-ctor' );
var scalar2ndarray = require( '@stdlib/ndarray-from-scalar' );
var ndarray2array = require( '@stdlib/ndarray-to-array' );
var ndarraylike2scalar = require( '@stdlib/ndarray-base-ndarraylike2scalar' );
var dindexOf = require( '@stdlib/blas-ext-base-ndarray-dindex-of' );

var xbuf = discreteUniform( 10, -100, 100, {
    'dtype': 'float64'
});
var x = new ndarray( 'float64', xbuf, [ xbuf.length ], [ 1 ], 0, 'row-major' );
console.log( ndarray2array( x ) );

var searchElement = scalar2ndarray( 80.0, {
    'dtype': 'float64'
});
console.log( 'Search Element:', ndarraylike2scalar( searchElement ) );

var fromIndex = scalar2ndarray( 0, {
    'dtype': 'generic'
});
console.log( 'From Index:', ndarraylike2scalar( fromIndex ) );

var idx = dindexOf( [ x, searchElement, fromIndex ] );
console.log( idx );
```

</section>

<!-- /.examples -->

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

<section class="related">

</section>

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* * *

## 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

[![Chat][chat-image]][chat-url]

---

## License

See [LICENSE][stdlib-license].


## Copyright

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

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