Return a double-precision floating-point number with the magnitude of x and the sign of y.
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> Return a [double-precision floating-point number][ieee754] with the magnitude of x and the sign of y.
``bash`
npm install @stdlib/math-base-special-copysign
`javascript`
var copysign = require( '@stdlib/math-base-special-copysign' );
#### copysign( x, y )
Returns a [double-precision floating-point number][ieee754] with the magnitude of x and the sign of y.
`javascript
var z = copysign( -3.14, 10.0 );
// returns 3.14
z = copysign( 3.14, -1.0 );
// returns -3.14
z = copysign( 1.0, -0.0 );
// returns -1.0
z = copysign( -3.14, -0.0 );
// returns -3.14
z = copysign( -0.0, 1.0 );
// returns 0.0
`
- According to the [IEEE754][ieee754] standard, a NaN has a biased exponent equal to 2047, a significand greater than 0, and a sign bit equal to either 1 or 0. In which case, NaN may not correspond to just one but many binary representations. Accordingly, care should be taken to ensure that y is not NaN; otherwise, behavior may be indeterminate.
`javascript
var uniform = require( '@stdlib/random-array-uniform' );
var logEachMap = require( '@stdlib/console-log-each-map' );
var copysign = require( '@stdlib/math-base-special-copysign' );
var opts = {
'dtype': 'float64'
};
var x = uniform( 100, -50.0, 50.0, opts );
var y = uniform( 100, -5.0, 5.0, opts );
// Generate random double-precision floating-point numbers x and y and copy the sign of y to x...`
logEachMap( 'x: %0.4f, y: %0.4f => %0.4f', x, y, copysign );
*
`c`
#include "stdlib/math/base/special/copysign.h"
#### stdlib_base_copysign( x, y )
Returns a [double-precision floating-point number][ieee754] with the magnitude of x and the sign of y.
`c
double v = stdlib_base_copysign( -3.14, 10.0 );
// returns 3.14
v = stdlib_base_copysign( 3.14, -1.0 );
// returns -3.14
`
The function accepts the following arguments:
- x: [in] double number from which to derive a magnitude.[in] double
- y: number from which to derive a sign.
`c`
double stdlib_base_copysign( const double x, const double y );
`c
#include "stdlib/math/base/special/copysign.h"
#include
int main( void ) {
const double x[] = { 3.14, -3.14, 0.0, 0.0/0.0 };
double y;
int i;
for ( i = 0; i < 4; i++ ) {
y = stdlib_base_copysign( x[ i ], -3.0 );
printf( "copysign(%lf, %lf) = %lf\n", x[ i ], -3.0, y );
}
}
`
*
- [@stdlib/math-base/special/flipsign][@stdlib/math/base/special/flipsign]: return a double-precision floating-point number with the magnitude of x and the sign of x\*y.
*
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].
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---
See [LICENSE][stdlib-license].
Copyright © 2016-2026. The Stdlib [Authors][stdlib-authors].
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[stdlib]: https://github.com/stdlib-js/stdlib
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[umd]: https://github.com/umdjs/umd
[es-module]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Modules
[deno-url]: https://github.com/stdlib-js/math-base-special-copysign/tree/deno
[deno-readme]: https://github.com/stdlib-js/math-base-special-copysign/blob/deno/README.md
[umd-url]: https://github.com/stdlib-js/math-base-special-copysign/tree/umd
[umd-readme]: https://github.com/stdlib-js/math-base-special-copysign/blob/umd/README.md
[esm-url]: https://github.com/stdlib-js/math-base-special-copysign/tree/esm
[esm-readme]: https://github.com/stdlib-js/math-base-special-copysign/blob/esm/README.md
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[ieee754]: https://en.wikipedia.org/wiki/IEEE_754-1985
[@stdlib/math/base/special/flipsign]: https://www.npmjs.com/package/@stdlib/math-base-special-flipsign