README.md (5097B)
1 <!-- 2 3 @license Apache-2.0 4 5 Copyright (c) 2020 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 # dcuminabs 22 23 > Calculate the cumulative minimum absolute value of double-precision floating-point strided array elements. 24 25 <section class="intro"> 26 27 </section> 28 29 <!-- /.intro --> 30 31 <section class="usage"> 32 33 ## Usage 34 35 ```javascript 36 var dcuminabs = require( '@stdlib/stats/base/dcuminabs' ); 37 ``` 38 39 #### dcuminabs( N, x, strideX, y, strideY ) 40 41 Computes the cumulative minimum absolute value of double-precision floating-point strided array elements. 42 43 ```javascript 44 var Float64Array = require( '@stdlib/array/float64' ); 45 46 var x = new Float64Array( [ 1.0, -2.0, 2.0 ] ); 47 var y = new Float64Array( x.length ); 48 49 dcuminabs( x.length, x, 1, y, 1 ); 50 // y => <Float64Array>[ 1.0, 1.0, 1.0 ] 51 ``` 52 53 The function has the following parameters: 54 55 - **N**: number of indexed elements. 56 - **x**: input [`Float64Array`][@stdlib/array/float64]. 57 - **strideX**: index increment for `x`. 58 - **y**: output [`Float64Array`][@stdlib/array/float64]. 59 - **strideY**: index increment for `y`. 60 61 The `N` and `stride` parameters determine which elements in `x` and `y` are accessed at runtime. For example, to compute the cumulative minimum absolute value of every other element in `x`, 62 63 ```javascript 64 var Float64Array = require( '@stdlib/array/float64' ); 65 66 var x = new Float64Array( [ 1.0, 2.0, 2.0, -7.0, -2.0, 3.0, 4.0, 2.0 ] ); 67 var y = new Float64Array( x.length ); 68 69 var v = dcuminabs( 4, x, 2, y, 1 ); 70 // y => <Float64Array>[ 1.0, 1.0, 1.0, 1.0, 0.0, 0.0, 0.0, 0.0 ] 71 ``` 72 73 Note that indexing is relative to the first index. To introduce an offset, use [`typed array`][mdn-typed-array] views. 74 75 <!-- eslint-disable stdlib/capitalized-comments --> 76 77 ```javascript 78 var Float64Array = require( '@stdlib/array/float64' ); 79 80 // Initial arrays... 81 var x0 = new Float64Array( [ 2.0, 1.0, 2.0, -2.0, -2.0, 2.0, 3.0, 4.0 ] ); 82 var y0 = new Float64Array( x0.length ); 83 84 // Create offset views... 85 var x1 = new Float64Array( x0.buffer, x0.BYTES_PER_ELEMENT*1 ); // start at 2nd element 86 var y1 = new Float64Array( y0.buffer, y0.BYTES_PER_ELEMENT*3 ); // start at 4th element 87 88 dcuminabs( 4, x1, -2, y1, 1 ); 89 // y0 => <Float64Array>[ 0.0, 0.0, 0.0, 4.0, 2.0, 2.0, 1.0, 0.0 ] 90 ``` 91 92 #### dcuminabs.ndarray( N, x, strideX, offsetX, y, strideY, offsetY ) 93 94 Computes the cumulative minimum absolute value of double-precision floating-point strided array elements using alternative indexing semantics. 95 96 ```javascript 97 var Float64Array = require( '@stdlib/array/float64' ); 98 99 var x = new Float64Array( [ 1.0, -2.0, 2.0 ] ); 100 var y = new Float64Array( x.length ); 101 102 dcuminabs.ndarray( x.length, x, 1, 0, y, 1, 0 ); 103 // y => <Float64Array>[ 1.0, 1.0, 1.0 ] 104 ``` 105 106 The function has the following additional parameters: 107 108 - **offsetX**: starting index for `x`. 109 - **offsetY**: starting index for `y`. 110 111 While [`typed array`][mdn-typed-array] views mandate a view offset based on the underlying `buffer`, `offsetX` and `offsetY` parameters support indexing semantics based on a starting indices. For example, to calculate the cumulative minimum absolute value of every other value in `x` starting from the second value and to store in the last `N` elements of `y` starting from the last element 112 113 ```javascript 114 var Float64Array = require( '@stdlib/array/float64' ); 115 116 var x = new Float64Array( [ 2.0, 1.0, 2.0, -2.0, -2.0, 2.0, 3.0, 4.0 ] ); 117 var y = new Float64Array( x.length ); 118 119 dcuminabs.ndarray( 4, x, 2, 1, y, -1, y.length-1 ); 120 // y => <Float64Array>[ 0.0, 0.0, 0.0, 0.0, 1.0, 1.0, 1.0, 1.0 ] 121 ``` 122 123 </section> 124 125 <!-- /.usage --> 126 127 <section class="notes"> 128 129 ## Notes 130 131 - If `N <= 0`, both functions return `y` unchanged. 132 133 </section> 134 135 <!-- /.notes --> 136 137 <section class="examples"> 138 139 ## Examples 140 141 <!-- eslint no-undef: "error" --> 142 143 ```javascript 144 var randu = require( '@stdlib/random/base/randu' ); 145 var round = require( '@stdlib/math/base/special/round' ); 146 var Float64Array = require( '@stdlib/array/float64' ); 147 var dcuminabs = require( '@stdlib/stats/base/dcuminabs' ); 148 149 var y; 150 var x; 151 var i; 152 153 x = new Float64Array( 10 ); 154 y = new Float64Array( x.length ); 155 for ( i = 0; i < x.length; i++ ) { 156 x[ i ] = round( (randu()*100.0) - 50.0 ); 157 } 158 console.log( x ); 159 console.log( y ); 160 161 dcuminabs( x.length, x, 1, y, -1 ); 162 console.log( y ); 163 ``` 164 165 </section> 166 167 <!-- /.examples --> 168 169 <section class="references"> 170 171 </section> 172 173 <!-- /.references --> 174 175 <section class="links"> 176 177 [@stdlib/array/float64]: https://www.npmjs.com/package/@stdlib/array-float64 178 179 [mdn-typed-array]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray 180 181 </section> 182 183 <!-- /.links -->