time-to-botec

README.md (5659B)

---

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 # nanmskmax
 
 > Calculate the maximum value of a strided array according to a mask, ignoring `NaN` values.
 
 <section class="intro">
 
 </section>
 
 <!-- /.intro -->
 
 <section class="usage">
 
 ## Usage
 
 ```javascript
 var nanmskmax = require( '@stdlib/stats/base/nanmskmax' );
 ```
 
 #### nanmskmax( N, x, strideX, mask, strideMask )
 
 Computes the maximum value of a strided array `x` according to a `mask`, ignoring `NaN` values.
 
 ```javascript
 var x = [ 1.0, -2.0, 4.0, 2.0, NaN ];
 var mask = [ 0, 0, 1, 0, 0 ];
 
 var v = nanmskmax( x.length, x, 1, mask, 1 );
 // returns 2.0
 ```
 
 The function has the following parameters:
 
 -   **N**: number of indexed elements.
 -   **x**: input [`Array`][mdn-array] or [`typed array`][mdn-typed-array].
 -   **strideX**: index increment for `x`.
 -   **mask**: mask [`Array`][mdn-array] or [`typed array`][mdn-typed-array]. If a `mask` array element is `0`, the corresponding element in `x` is considered valid and **included** in computation. If a `mask` array element is `1`, the corresponding element in `x` is considered invalid/missing and **excluded** from computation.
 -   **strideMask**: index increment for `mask`.
 
 The `N` and `stride` parameters determine which elements are accessed at runtime. For example, to compute the maximum value of every other element in `x`,
 
 ```javascript
 var floor = require( '@stdlib/math/base/special/floor' );
 
 var x = [ 1.0, 2.0, -7.0, -2.0, 4.0, 3.0, 5.0, 6.0 ];
 var mask = [ 0, 0, 0, 0, 0, 0, 1, 1 ];
 var N = floor( x.length / 2 );
 
 var v = nanmskmax( N, x, 2, mask, 2 );
 // returns 4.0
 ```
 
 Note that indexing is relative to the first index. To introduce offsets, use [`typed array`][mdn-typed-array] views.
 
 <!-- eslint-disable stdlib/capitalized-comments -->
 
 ```javascript
 var Float64Array = require( '@stdlib/array/float64' );
 var Uint8Array = require( '@stdlib/array/uint8' );
 var floor = require( '@stdlib/math/base/special/floor' );
 
 var x0 = new Float64Array( [ 2.0, 1.0, -2.0, -2.0, 3.0, 4.0, 5.0, 6.0 ] );
 var x1 = new Float64Array( x0.buffer, x0.BYTES_PER_ELEMENT*1 ); // start at 2nd element
 
 var mask0 = new Uint8Array( [ 0, 0, 0, 0, 0, 0, 1, 1 ] );
 var mask1 = new Uint8Array( mask0.buffer, mask0.BYTES_PER_ELEMENT*1 ); // start at 2nd element
 
 var N = floor( x0.length / 2 );
 
 var v = nanmskmax( N, x1, 2, mask1, 2 );
 // returns 4.0
 ```
 
 #### nanmskmax.ndarray( N, x, strideX, offsetX, mask, strideMask, offsetMask )
 
 Computes the maximum value of a strided array according to a `mask`, ignoring `NaN` values and using alternative indexing semantics.
 
 ```javascript
 var x = [ 1.0, -2.0, 4.0, 2.0, NaN ];
 var mask = [ 0, 0, 1, 0, 0 ];
 
 var v = nanmskmax.ndarray( x.length, x, 1, 0, mask, 1, 0 );
 // returns 2.0
 ```
 
 The function has the following additional parameters:
 
 -   **offsetX**: starting index for `x`.
 -   **offsetMask**: starting index for `mask`.
 
 While [`typed array`][mdn-typed-array] views mandate a view offset based on the underlying `buffer`, the `offset` parameter supports indexing semantics based on a starting index. For example, to calculate the maximum value for every other value in `x` starting from the second value
 
 ```javascript
 var floor = require( '@stdlib/math/base/special/floor' );
 
 var x = [ 2.0, 1.0, -2.0, -2.0, 3.0, 4.0, 5.0, 6.0 ];
 var mask = [ 0, 0, 0, 0, 0, 0, 1, 1 ];
 var N = floor( x.length / 2 );
 
 var v = nanmskmax.ndarray( N, x, 2, 1, mask, 2, 1 );
 // returns 4.0
 ```
 
 </section>
 
 <!-- /.usage -->
 
 <section class="notes">
 
 ## Notes
 
 -   If `N <= 0`, both functions return `NaN`.
 -   Depending on the environment, the typed versions ([`dnanmskmax`][@stdlib/stats/base/dnanmskmax], [`snanmskmax`][@stdlib/stats/base/snanmskmax], etc.) are likely to be significantly more performant.
 
 </section>
 
 <!-- /.notes -->
 
 <section class="examples">
 
 ## Examples
 
 <!-- eslint no-undef: "error" -->
 
 ```javascript
 var randu = require( '@stdlib/random/base/randu' );
 var round = require( '@stdlib/math/base/special/round' );
 var Float64Array = require( '@stdlib/array/float64' );
 var Uint8Array = require( '@stdlib/array/uint8' );
 var nanmskmax = require( '@stdlib/stats/base/nanmskmax' );
 
 var mask;
 var x;
 var i;
 
 x = new Float64Array( 10 );
 mask = new Uint8Array( x.length );
 for ( i = 0; i < x.length; i++ ) {
     if ( randu() < 0.2 ) {
         mask[ i ] = 1;
     } else {
         mask[ i ] = 0;
     }
     if ( randu() < 0.1 ) {
         x[ i ] = NaN;
     } else {
         x[ i ] = round( (randu()*100.0) - 50.0 );
     }
 }
 console.log( x );
 console.log( mask );
 
 var v = nanmskmax( x.length, x, 1, mask, 1 );
 console.log( v );
 ```
 
 </section>
 
 <!-- /.examples -->
 
 <section class="links">
 
 [mdn-array]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array
 
 [mdn-typed-array]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray
 
 [@stdlib/stats/base/dnanmskmax]: https://www.npmjs.com/package/@stdlib/stats/tree/main/base/dnanmskmax
 
 [@stdlib/stats/base/snanmskmax]: https://www.npmjs.com/package/@stdlib/stats/tree/main/base/snanmskmax
 
 </section>
 
 <!-- /.links -->