npm install @stdlib/ndarray-filter-map

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To view installation and usage instructions specific to each branch build, be sure to explicitly navigate to the respective README files on each branch, as linked to above.

varfilterMap=require('@stdlib/ndarray-filter-map');

Filters and maps elements in an inputndarray to elements in a new outputndarray according to a callback function.

varFloat64Array=require('@stdlib/array-float64');varndarray=require('@stdlib/ndarray-ctor');varndarray2array=require('@stdlib/ndarray-to-array');functionfcn(z){if(z>5.0){returnz*10.0;}}varbuffer=newFloat64Array([1.0,2.0,3.0,4.0,5.0,6.0,7.0,8.0,9.0,10.0,11.0,12.0]);varshape=[2,3];varstrides=[6,1];varoffset=1;varx=ndarray('float64',buffer,shape,strides,offset,'row-major');// returns <ndarray>vary=filterMap(x,fcn);// returns <ndarray>vararr=ndarray2array(y);// returns [ 80.0, 90.0, 100.0 ]

The function accepts the following arguments:

• x: inputndarray.
• options: function options(optional).
• fcn: callback function.
• thisArg: callback function execution context(optional).

The function accepts the following options:

• dtype: output ndarraydata type. If not specified, the output ndarraydata type is inferred from the inputndarray.
• order: index iteration order. By default, the function iterates over elements according to thelayout order of the providedndarray. Accordingly, for row-major inputndarrays, the last dimension indices increment fastest. For column-major inputndarrays, the first dimension indices increment fastest. To override the inferred order and ensure that indices increment in a specific manner, regardless of the inputndarray's layout order, explicitly set the iteration order. Note, however, that iterating according to an order which does not match that of the inputndarray may, in some circumstances, result in performance degradation due to cache misses. Must be either'row-major' or'column-major'.

By default, the output ndarraydata type is inferred from the inputndarray. To return an ndarray with a differentdata type, specify thedtype option.

varFloat64Array=require('@stdlib/array-float64');varndarray=require('@stdlib/ndarray-ctor');vardtype=require('@stdlib/ndarray-dtype');varndarray2array=require('@stdlib/ndarray-to-array');functionfcn(z){if(z>5.0){returnz*10.0;}}varbuffer=newFloat64Array([1.0,2.0,3.0,4.0,5.0,6.0,7.0,8.0,9.0,10.0,11.0,12.0]);varshape=[2,3];varstrides=[6,1];varoffset=1;varx=ndarray('float64',buffer,shape,strides,offset,'row-major');// returns <ndarray>varopts={'dtype':'float32'};vary=filterMap(x,opts,fcn);// returns <ndarray>vardt=dtype(y);// returns 'float32'vararr=ndarray2array(y);// returns [ 80.0, 90.0, 100.0 ]

To set the callback function execution context, provide athisArg.

varFloat64Array=require('@stdlib/array-float64');varndarray=require('@stdlib/ndarray-ctor');varndarray2array=require('@stdlib/ndarray-to-array');functionfcn(z){this.count+=1;if(z>5.0){returnz*10.0;}}varbuffer=newFloat64Array([1.0,2.0,3.0,4.0,5.0,6.0,7.0,8.0,9.0,10.0,11.0,12.0]);varshape=[2,3];varstrides=[6,1];varoffset=1;varx=ndarray('float64',buffer,shape,strides,offset,'row-major');// returns <ndarray>varctx={'count':0};vary=filterMap(x,fcn,ctx);// returns <ndarray>vararr=ndarray2array(y);// returns [ 80.0, 90.0, 100.0 ]varcount=ctx.count;// returns 6

The callback function is provided the following arguments:

• value: current array element.
• indices: current array element indices.
• arr: the inputndarray.

• The function doesnot perform explicit casting (e.g., from a real-valued floating-point number to a complex floating-point number). Any such casting should be performed by a provided callback function.

  varFloat64Array=require('@stdlib/array-float64');varndarray=require('@stdlib/ndarray-ctor');varComplex128=require('@stdlib/complex-float64-ctor');varndarray2array=require('@stdlib/ndarray-to-array');functionfcn(z){if(z>5.0){returnnewComplex128(z,0.0);}}varbuffer=newFloat64Array([1.0,2.0,3.0,4.0,5.0,6.0,7.0,8.0,9.0,10.0,11.0,12.0]);varshape=[2,3];varstrides=[6,1];varoffset=1;varx=ndarray('float64',buffer,shape,strides,offset,'row-major');// returns <ndarray>varopts={'dtype':'complex128'};vary=filterMap(x,opts,fcn);// returns <ndarray>

• If a provided callback function returnsundefined, the function skips the respectivendarray element. If the callback function returns a value other thanundefined, the function stores the callback's return value in the outputndarray.

• The functionalways returns a one-dimensionalndarray.

• @stdlib/ndarray-filter:return a shallow copy of an ndarray containing only those elements which pass a test implemented by a predicate function.
• @stdlib/ndarray-map:apply a callback to elements in an input ndarray and assign results to elements in a new output ndarray.
• @stdlib/ndarray-reject:return a shallow copy of an ndarray containing only those elements which fail a test implemented by a predicate function.
• @stdlib/ndarray-slice:return a read-only view of an input ndarray.

This package is part ofstdlib, a standard library for JavaScript and Node.js, with an emphasis on numerical and scientific computing. The library provides a collection of robust, high performance libraries for mathematics, statistics, streams, utilities, and more.

For more information on the project, filing bug reports and feature requests, and guidance on how to developstdlib, see the main projectrepository.

SeeLICENSE.

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