time-to-botec

Benchmark sampling in different programming languages
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README.md (3578B)

      1 <!--
      2 
      3 @license Apache-2.0
      4 
      5 Copyright (c) 2018 The Stdlib Authors.
      6 
      7 Licensed under the Apache License, Version 2.0 (the "License");
      8 you may not use this file except in compliance with the License.
      9 You may obtain a copy of the License at
     10 
     11    http://www.apache.org/licenses/LICENSE-2.0
     12 
     13 Unless required by applicable law or agreed to in writing, software
     14 distributed under the License is distributed on an "AS IS" BASIS,
     15 WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     16 See the License for the specific language governing permissions and
     17 limitations under the License.
     18 
     19 -->
     20 
     21 # incrstdev
     22 
     23 > Compute a [corrected sample standard deviation][sample-stdev] incrementally.
     24 
     25 <section class="intro">
     26 
     27 The [corrected sample standard deviation][sample-stdev] is defined as
     28 
     29 <!-- <equation class="equation" label="eq:corrected_sample_standard_deviation" align="center" raw="s = \sqrt{\frac{1}{n-1} \sum_{i=0}^{n-1} ( x_i - \bar{x} )^2}" alt="Equation for the corrected sample standard deviation."> -->
     30 
     31 <div class="equation" align="center" data-raw-text="s = \sqrt{\frac{1}{n-1} \sum_{i=0}^{n-1} ( x_i - \bar{x} )^2}" data-equation="eq:corrected_sample_standard_deviation">
     32     <img src="https://cdn.jsdelivr.net/gh/stdlib-js/stdlib@49d8cabda84033d55d7b8069f19ee3dd8b8d1496/lib/node_modules/@stdlib/stats/incr/stdev/docs/img/equation_corrected_sample_standard_deviation.svg" alt="Equation for the corrected sample standard deviation.">
     33     <br>
     34 </div>
     35 
     36 <!-- </equation> -->
     37 
     38 </section>
     39 
     40 <!-- /.intro -->
     41 
     42 <section class="usage">
     43 
     44 ## Usage
     45 
     46 ```javascript
     47 var incrstdev = require( '@stdlib/stats/incr/stdev' );
     48 ```
     49 
     50 #### incrstdev( \[mean] )
     51 
     52 Returns an accumulator `function` which incrementally computes a [corrected sample standard deviation][sample-stdev].
     53 
     54 ```javascript
     55 var accumulator = incrstdev();
     56 ```
     57 
     58 If the mean is already known, provide a `mean` argument.
     59 
     60 ```javascript
     61 var accumulator = incrstdev( 3.0 );
     62 ```
     63 
     64 #### accumulator( \[x] )
     65 
     66 If provided an input value `x`, the accumulator function returns an updated [corrected sample standard deviation][sample-stdev]. If not provided an input value `x`, the accumulator function returns the current [corrected sample standard deviation][sample-stdev].
     67 
     68 ```javascript
     69 var accumulator = incrstdev();
     70 
     71 var s = accumulator( 2.0 );
     72 // returns 0.0
     73 
     74 s = accumulator( 1.0 ); // => sqrt(((2-1.5)^2+(1-1.5)^2) / (2-1))
     75 // returns ~0.7071
     76 
     77 s = accumulator( 3.0 ); // => sqrt(((2-2)^2+(1-2)^2+(3-2)^2) / (3-1))
     78 // returns 1.0
     79 
     80 s = accumulator();
     81 // returns 1.0
     82 ```
     83 
     84 </section>
     85 
     86 <!-- /.usage -->
     87 
     88 <section class="notes">
     89 
     90 ## Notes
     91 
     92 -   Input values are **not** type checked. If provided `NaN` or a value which, when used in computations, results in `NaN`, the accumulated value is `NaN` for **all** future invocations. If non-numeric inputs are possible, you are advised to type check and handle accordingly **before** passing the value to the accumulator function.
     93 
     94 </section>
     95 
     96 <!-- /.notes -->
     97 
     98 <section class="examples">
     99 
    100 ## Examples
    101 
    102 <!-- eslint no-undef: "error" -->
    103 
    104 ```javascript
    105 var randu = require( '@stdlib/random/base/randu' );
    106 var incrstdev = require( '@stdlib/stats/incr/stdev' );
    107 
    108 var accumulator;
    109 var v;
    110 var i;
    111 
    112 // Initialize an accumulator:
    113 accumulator = incrstdev();
    114 
    115 // For each simulated datum, update the sample standard deviation...
    116 for ( i = 0; i < 100; i++ ) {
    117     v = randu() * 100.0;
    118     accumulator( v );
    119 }
    120 console.log( accumulator() );
    121 ```
    122 
    123 </section>
    124 
    125 <!-- /.examples -->
    126 
    127 <section class="links">
    128 
    129 [sample-stdev]: https://en.wikipedia.org/wiki/Standard_deviation
    130 
    131 </section>
    132 
    133 <!-- /.links -->