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roundn
Round a doubleprecision floatingpoint number to the nearest multiple of 10^n.
Installation
npm install @stdlib/mathbasespecialroundn
Usage
var roundn = require( '@stdlib/mathbasespecialroundn' );
roundn( x, n )
Rounds a doubleprecision floatingpoint 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 floatingpoint 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/randombaserandu' );
var roundn = require( '@stdlib/mathbasespecialroundn' );
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 doubleprecision floatingpoint 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/mathbase/special/ceiln
: round a numeric value to the nearest multiple of 10^n toward positive infinity. 
@stdlib/mathbase/special/floorn
: round a doubleprecision floatingpoint number to the nearest multiple of 10^n toward negative infinity. 
@stdlib/mathbase/special/round
: round a numeric value to the nearest integer. 
@stdlib/mathbase/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 © 20162024. The Stdlib Authors.