Unary
Apply a unary callback to elements in an input ndarray and assign results to elements in an output ndarray.
Usage
var unary = require( '@stdlib/ndarray/base/unary' );
unary( arrays, fcn )
Applies a unary callback to elements in an input ndarray and assigns results to elements in an output ndarray.
var Float64Array = require( '@stdlib/array/float64' );
function scale( x ) {
return x * 10.0;
}
// Create data buffers:
var xbuf = new Float64Array( [ 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0, 9.0, 10.0, 11.0, 12.0 ] );
var ybuf = new Float64Array( 6 );
// Define the shape of the input and output arrays:
var shape = [ 3, 1, 2 ];
// Define the array strides:
var sx = [ 4, 4, 1 ];
var sy = [ 2, 2, 1 ];
// Define the index offsets:
var ox = 1;
var oy = 0;
// Create the input and output ndarray-like objects:
var x = {
'dtype': 'float64',
'data': xbuf,
'shape': shape,
'strides': sx,
'offset': ox,
'order': 'row-major'
};
var y = {
'dtype': 'float64',
'data': ybuf,
'shape': shape,
'strides': sy,
'offset': oy,
'order': 'row-major'
};
// Apply the unary function:
unary( [ x, y ], scale );
console.log( y.data );
// => <Float64Array>[ 20.0, 30.0, 60.0, 70.0, 100.0, 110.0 ]
The function accepts the following arguments:
- arrays: array-like object containing one input ndarray and one output ndarray.
- fcn: unary function to apply.
Each provided ndarray should be an object with the following properties:
- dtype: data type.
- data: data buffer.
- shape: dimensions.
- strides: stride lengths.
- offset: index offset.
- order: specifies whether an ndarray is row-major (C-style) or column major (Fortran-style).
Notes
- For very high-dimensional ndarrays which are non-contiguous, one should consider copying the underlying data to contiguous memory before applying a unary function in order to achieve better performance.
Examples
var discreteUniform = require( '@stdlib/random/base/discrete-uniform' ).factory;
var filledarray = require( '@stdlib/array/filled' );
var filledarrayBy = require( '@stdlib/array/filled-by' );
var shape2strides = require( '@stdlib/ndarray/base/shape2strides' );
var ndarray2array = require( '@stdlib/ndarray/base/to-array' );
var unary = require( '@stdlib/ndarray/base/unary' );
function scale( x ) {
return x * 10;
}
var N = 10;
var x = {
'dtype': 'generic',
'data': filledarrayBy( N, 'generic', discreteUniform( -100, 100 ) ),
'shape': [ 5, 2 ],
'strides': [ 2, 1 ],
'offset': 0,
'order': 'row-major'
};
var y = {
'dtype': 'generic',
'data': filledarray( 0, N, 'generic' ),
'shape': x.shape.slice(),
'strides': shape2strides( x.shape, 'column-major' ),
'offset': 0,
'order': 'column-major'
};
unary( [ x, y ], scale );
console.log( ndarray2array( x.data, x.shape, x.strides, x.offset, x.order ) );
console.log( ndarray2array( y.data, y.shape, y.strides, y.offset, y.order ) );
C APIs
Character codes for data types:
- d:
float64(double-precision floating-point number). - f:
float32(single-precision floating-point number). - c:
complex64(single-precision floating-point complex number). - z:
complex128(double-precision floating-point complex number). - s:
int8(signed 8-bit integer). - b:
uint8(unsigned 8-bit integer). - k:
int16(signed 16-bit integer). - t:
uint16(unsigned 16-bit integer). - i:
int32(signed 32-bit integer). - u:
uint32(unsigned 32-bit integer). - l:
int64(signed 64-bit integer). - v:
uint64(unsigned 64-bit integer). - x:
boolean.
Function name suffix naming convention:
stdlib_ndarray_<input_data_type>_<output_data_type>[_as_<callback_arg_data_type>_<callback_return_data_type>]
For example,
void stdlib_ndarray_d_d(...) {...}
is a function which accepts one double-precision floating-point input ndarray and one double-precision floating-point output ndarray. In other words, the suffix encodes the function type signature.
To support callbacks whose input arguments and/or return values are of a different data type than the input and/or output ndarray data types, the naming convention supports appending an as suffix. For example,
void stdlib_ndarray_f_f_as_d_d(...) {...}
is a function which accepts one single-precision floating-point input ndarray and one single-precision floating-point output ndarray. However, the callback accepts and returns double-precision floating-point numbers. Accordingly, the input and output values need to be cast using the following conversion sequence
// Convert each input array element to double-precision:
double dxi = (double)fx[ i ];
// Evaluate the callback:
double dyi = f( dxi );
// Convert the callback return value to single-precision:
fy[ i ] = (float)dyi;
Usage
#include "stdlib/ndarray/base/unary.h"
FIXME: add docs for the loop interfaces
Examples
// FIXME: add example