roundn

Round a double-precision floating-point number to the nearest multiple of 10^n.

Installation

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

Usage

var roundn = require( '@stdlib/math-base-special-roundn' );

roundn( x, n )

Rounds a double-precision floating-point number to the nearest multiple of 10^n.

// Round a value to 2 decimal places:
var v = roundn( 3.141592653589793, -2 );
// returns 3.14

// If n = 0, `roundn` behaves like `round`:
v = roundn( 3.141592653589793, 0 );
// returns 3.0

// Round a value to the nearest thousand:
v = roundn( 12368.0, 3 );
// returns 12000.0

Notes

• When operating on floating-point numbers in bases other than 2, rounding to specified digits can be inexact. For example,

  var x = 0.2 + 0.1;
  // returns 0.30000000000000004
  
  // Should round to 0.3...
  var v = roundn( x, -16 );
  // returns 0.3000000000000001

Examples

var randu = require( '@stdlib/random-base-randu' );
var roundn = require( '@stdlib/math-base-special-roundn' );

var x;
var n;
var v;
var i;

for ( i = 0; i < 100; i++ ) {
    x = (randu()*100.0) - 50.0;
    n = roundn( randu()*5.0, 0 );
    v = roundn( x, -n );
    console.log( 'x: %d. Number of decimals: %d. Rounded: %d.', x, n, v );
}

C APIs

Usage

#include "stdlib/math/base/special/roundn.h"

stdlib_base_roundn( x, n )

Rounds a double-precision floating-point number to the nearest multiple of 10^n.

double y = stdlib_base_roundn( 3.14, -2 );
// returns 3.14

The function accepts the following arguments:

• x: [in] double input value.
• n: [in] int32_t integer power of 10.

double stdlib_base_roundn( const double x, const int32_t n );

Examples

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

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_roundn( x[ i ], -2 );
        printf( "roundn(%lf) = %lf\n", x[ i ], y );
    }
}

See Also

• @stdlib/math-base/special/ceiln: round a numeric value to the nearest multiple of 10^n toward positive infinity.
• @stdlib/math-base/special/floorn: round a double-precision floating-point number to the nearest multiple of 10^n toward negative infinity.
• @stdlib/math-base/special/round: round a numeric value to the nearest integer.
• @stdlib/math-base/special/roundb: round a numeric value to the nearest multiple of b^n on a linear scale.

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.

Community

License

See LICENSE.

Copyright

Copyright © 2016-2024. The Stdlib Authors.