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atan2

README.md

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).

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