floorb

Round a numeric value to the nearest multiple of b^n toward negative infinity.

Installation

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

Alternatively,

To load the package in a website via a script tag without installation and bundlers, use the ES Module available on the esm branch (see README).
If you are using Deno, visit the deno branch (see README for usage intructions).
For use in Observable, or in browser/node environments, use the Universal Module Definition (UMD) build available on the umd branch (see README).

The branches.md file summarizes the available branches and displays a diagram illustrating their relationships.

To view installation and usage instructions specific to each branch build, be sure to explicitly navigate to the respective README files on each branch, as linked to above.

Usage

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

floorb( x, n, b )

Rounds a numeric value to the nearest multiple of b^n toward negative infinity.

// Round a value to 4 decimal places:
var v = floorb( 3.141592653589793, -4, 10 );
// returns 3.1415

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

// Round a value to the nearest multiple of two toward negative infinity:
v = floorb( 5.0, 1, 2 );
// returns 4.0

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

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 = floorb( 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/floorb.h"

stdlib_base_floorb( x, n, b )

Rounds a numeric value to the nearest multiple of b^n toward negative infinity.

double out = stdlib_base_floorb( 3.141592653589793, -4, 10 );
// returns 3.1415

The function accepts the following arguments:

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

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

Examples

#include "stdlib/math/base/special/floorb.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_floorb( x[ i ], n[ i ], b[ i ] );
        printf( "floorb(%lf, %d, %d) = %lf\n", x[ i ], n[ i ], b[ i ], v );
    }
}

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.