112 lines
2.3 KiB
Markdown
112 lines
2.3 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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# roundb
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> Round a numeric value to the nearest multiple of b^n on a linear scale.
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<section class="usage">
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## Usage
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```javascript
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var roundb = require( '@stdlib/math/base/special/roundb' );
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```
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#### roundb( x, n, b )
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Rounds a `numeric` value to the nearest multiple of `b^n` on a linear scale.
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```javascript
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// Round a value to 2 decimal places:
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var v = roundb( 3.141592653589793, -2, 10 );
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// returns 3.14
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// If n = 0 or b = 1, `roundb` behaves like `round`:
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v = roundb( 3.141592653589793, 0, 2 );
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// returns 3.0
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// Round a value to the nearest multiple of two:
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v = roundb( 5.0, 1, 2 );
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// returns 6.0
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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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- Due to rounding error in [floating-point numbers][ieee754], rounding may **not** be exact. 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 = roundb( x, -16, 10 );
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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 round = require( '@stdlib/math/base/special/round' );
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var pow = require( '@stdlib/math/base/special/pow' );
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var roundb = require( '@stdlib/math/base/special/roundb' );
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var x;
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var n;
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var b;
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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 = round( (randu()*10.0) - 5.0 );
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b = round( randu()*10.0 );
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v = roundb( x, n, b );
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console.log( 'x: %d. %d^%d: %d. Rounded: %d.', x, b, n, pow( b, 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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