npm package: @stdlib/math-base-special-atan2
Description: Compute the angle in the plane (in radians) between the positive x-axis and the ray from (0,0) to the point (x,y).
Author: The Stdlib Authors
Latest version: 0.3.1

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# atan2

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> Compute the angle in the plane (in radians) between the positive x-axis and the ray from `(0,0)` to the point `(x,y)`.

<section class="installation">

## Installation

```bash
npm install @stdlib/math-base-special-atan2
```

</section>

<section class="usage">

## Usage

```javascript
var atan2 = require( '@stdlib/math-base-special-atan2' );
```

#### atan2( y, x )

Computes the angle in the plane (in radians) between the positive x-axis and the ray from `(0,0)` to the point `(x,y)`.

```javascript
var v = atan2( 2.0, 2.0 ); // => atan(1.0)
// returns ~0.785

v = atan2( 6.0, 2.0 ); // => atan(3.0)
// returns ~1.249

v = atan2( -1.0, -1.0 ); // => atan(1.0) - π
// returns ~-2.356

v = atan2( 3.0, 0.0 ); // => π/2
// returns ~1.571

v = atan2( -2.0, 0.0 ); // => -π/2
// returns ~-1.571

v = atan2( 0.0, 0.0 );
// returns 0.0

v = atan2( 3.0, NaN );
// returns NaN
```

</section>

<!-- /.usage -->

<section class="examples">

## Examples

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

```javascript
var uniform = require( '@stdlib/random-array-uniform' );
var logEachMap = require( '@stdlib/console-log-each-map' );
var atan2 = require( '@stdlib/math-base-special-atan2' );

var opts = {
    'dtype': 'float64'
};
var x = uniform( 100, 0.0, 100.0, opts );
var y = uniform( 100, 0.0, 100.0, opts );

logEachMap( 'atan2(%0.4f,%0.4f) = %0.4f', y, x, atan2 );
```

</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/math/base/special/atan2.h"
```

#### stdlib_base_atan2( y, x )

Computes the angle in the plane (in radians) between the positive x-axis and the ray from `(0,0)` to the point `(x,y)`.

```c
double out = stdlib_base_atan2( 2.0, 2.0 );
// returns ~0.785

out = stdlib_base_atan2( 6.0, 2.0 );
// returns ~1.249
```

The function accepts the following arguments:

-   **y**: `[in] double` - `y` coordinate.
-   **x**: `[in] double` - `x` coordinate.

```c
double stdlib_base_atan2( const double y, const double x );
```

</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/math/base/special/atan2.h"
#include <stdlib.h>
#include <stdio.h>

int main( void ) {
    double y;
    double x;
    double v;
    int i;

    for ( i = 0; i < 100; i++ ) {
        y = ( ( (double)rand() / (double)RAND_MAX ) * 100.0 );
        x = ( ( (double)rand() / (double)RAND_MAX ) * 100.0 );
        v = stdlib_base_atan2( y, x );
        printf( "atan2(%lf, %lf) = %lf\n", y, x, v );
    }
    return 0;
}
```

</section>

<!-- /.examples -->

</section>

<!-- /.c -->

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

<section class="related">

* * *

## See Also

-   <span class="package-name">[`@stdlib/math-base/special/atan`][@stdlib/math/base/special/atan]</span><span class="delimiter">: </span><span class="description">compute the arctangent of a double-precision floating-point number.</span>

</section>

<!-- /.related -->

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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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---

## Copyright

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

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[@stdlib/math/base/special/atan]: https://www.npmjs.com/package/@stdlib/math-base-special-atan

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