108 lines
2.1 KiB
Markdown
108 lines
2.1 KiB
Markdown
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@license Apache-2.0
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Copyright (c) 2018 The Stdlib Authors.
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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-->
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# roundn
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> Round a numeric value to the nearest multiple of 10^n.
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<section class="usage">
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## Usage
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```javascript
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var roundn = require( '@stdlib/math/base/special/roundn' );
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```
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#### roundn( x, n )
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Rounds a `numeric` value to the nearest multiple of `10^n`.
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```javascript
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// Round a value to 2 decimal places:
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var v = roundn( 3.141592653589793, -2 );
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// returns 3.14
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// If n = 0, `roundn` behaves like `round`:
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v = roundn( 3.141592653589793, 0 );
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// returns 3.0
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// Round a value to the nearest thousand:
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v = roundn( 12368.0, 3 );
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// returns 12000.0
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```
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</section>
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<!-- /.usage -->
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<section class="notes">
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## Notes
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- When operating on [floating-point numbers][ieee754] in bases other than `2`, rounding to specified digits can be **inexact**. For example,
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```javascript
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var x = 0.2 + 0.1;
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// returns 0.30000000000000004
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// Should round to 0.3...
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var v = roundn( x, -16 );
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// returns 0.3000000000000001
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```
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</section>
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<!-- /.notes -->
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<section class="examples">
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## Examples
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<!-- eslint no-undef: "error" -->
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```javascript
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var randu = require( '@stdlib/random/base/randu' );
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var roundn = require( '@stdlib/math/base/special/roundn' );
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var x;
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var n;
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var v;
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var i;
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for ( i = 0; i < 100; i++ ) {
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x = (randu()*100.0) - 50.0;
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n = roundn( randu()*5.0, 0 );
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v = roundn( x, -n );
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console.log( 'x: %d. Number of decimals: %d. Rounded: %d.', x, n, v );
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}
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```
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</section>
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<!-- /.examples -->
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<section class="links">
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[ieee754]: https://en.wikipedia.org/wiki/IEEE_754-1985
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</section>
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<!-- /.links -->
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