atan2

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

Installation

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

Usage

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).

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

Examples

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 );

C APIs

Usage

#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).

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.

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

Examples

#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;
}

See Also

• @stdlib/math-base/special/atan: compute the arctangent of a double-precision floating-point number.

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.

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Copyright

Copyright © 2016-2026. The Stdlib Authors.