roundb

Round a numeric value to the nearest multiple of b^n on a linear scale.

Installation

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

Usage

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

roundb( x, n, b )

Rounds a numeric value to the nearest multiple of b^n on a linear scale.

// Round a value to 2 decimal places:
var v = roundb( 3.141592653589793, -2, 10 );
// returns 3.14

// If n = 0 or b = 1, `roundb` behaves like `round`:
v = roundb( 3.141592653589793, 0, 2 );
// returns 3.0

// Round a value to the nearest multiple of two:
v = roundb( 5.0, 1, 2 );
// returns 6.0

Notes

• Due to rounding error in floating-point numbers, rounding may not be exact. For example,

  var x = 0.2 + 0.1;
  // returns 0.30000000000000004
  
  // Should round to 0.3...
  var v = roundb( x, -16, 10 );
  // returns 0.3000000000000001

Examples

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

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

for ( i = 0; i < 100; i++ ) {
    x = (randu()*100.0) - 50.0;
    n = round( (randu()*10.0) - 5.0 );
    b = round( randu()*10.0 );
    v = roundb( x, n, b );
    console.log( 'x: %d. %d^%d: %d. Rounded: %d.', x, b, n, pow( b, n ), v );
}

Usage

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

stdlib_base_roundb( x, n, b )

Rounds a numeric value to the nearest multiple of b^n on a linear scale.

double out = stdlib_base_roundb( 3.141592653589793, -2, 10 );
// returns 3.14

The function accepts the following arguments:

• x: [in] double input value.
• n: [in] int32_t power.
• b: [in] int32_t base.

double stdlib_base_roundb( const double x, const int32_t n, const int32_t b );

Examples

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

int main( void ) {
    const double x[] = { -5.0, -3.89, -2.78, -1.67, -0.56, 0.56, 1.67, 2.78, 3.89, 5.0 };
    const int32_t n[] = { -4, -3, -2, -1, 0, 1, 2, 3, 4, 5 };
    const int32_t b[] = { 20, 19, 18, 17, 16, 15, 14, 13, 12, 11 };

    double v;
    int i;
    for ( i = 0; i < 10; i++ ) {
        v = stdlib_base_roundb( x[ i ], n[ i ], b[ i ] );
        printf( "roundb(%lf, %d, %d) = %lf\n", x[ i ], n[ i ], b[ i ], v );
    }
}

See Also

• @stdlib/math-base/special/ceilb: round a numeric value to the nearest multiple of b^n toward positive infinity.
• @stdlib/math-base/special/floorb: round a numeric value to the nearest multiple of b^n toward negative infinity.
• @stdlib/math-base/special/round: round a numeric value to the nearest integer.
• @stdlib/math-base/special/roundn: round a double-precision floating-point number to the nearest multiple of 10^n.

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.