# roundb

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

## 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 );
}
``````