Flatten an ndarray according to a callback function.
var flattenBy = require( '@stdlib/ndarray/flatten-by' );Flattens an ndarray according to a callback function.
var array = require( '@stdlib/ndarray/array' );
function scale( value ) {
return value * 2.0;
}
var x = array( [ [ [ 1.0, 2.0 ] ], [ [ 3.0, 4.0 ] ], [ [ 5.0, 6.0 ] ] ] );
// returns <ndarray>
var y = flattenBy( x, scale );
// returns <ndarray>[ 2.0, 4.0, 6.0, 8.0, 10.0, 12.0 ]The function accepts the following arguments:
- x: input ndarray.
- options: function options (optional).
- fcn: callback function.
- thisArg: callback execution context (optional).
The function accepts the following options:
-
order: order in which input ndarray elements should be flattened. Must be one of the following:
'row-major': flatten elements in lexicographic order. For example, given a two-dimensional input ndarray (i.e., a matrix), flattening in lexicographic order means flattening the input ndarray row-by-row.'column-major': flatten elements in colexicographic order. For example, given a two-dimensional input ndarray (i.e., a matrix), flattening in colexicographic order means flattening the input ndarray column-by-column.'any': flatten according to the physical layout of the input ndarray data in memory, regardless of the stated order of the input ndarray.'same': flatten according to the stated order of the input ndarray.
Default:
'row-major'. -
depth: maximum number of input ndarray dimensions to flatten.
-
dtype: output ndarray data type. By default, the function returns an ndarray having the same data type as a provided input ndarray.
By default, the function flattens all dimensions of the input ndarray. To flatten to a desired depth, specify the depth option.
var array = require( '@stdlib/ndarray/array' );
function scale( value ) {
return value * 2.0;
}
var x = array( [ [ [ 1.0, 2.0 ] ], [ [ 3.0, 4.0 ] ], [ [ 5.0, 6.0 ] ] ] );
// returns <ndarray>
var opts = {
'depth': 1
};
var y = flattenBy( x, opts, scale );
// returns <ndarray>[ [ 2.0, 4.0 ], [ 6.0, 8.0 ], [ 10.0, 12.0 ] ]By default, the input ndarray is flattened in lexicographic order. To flatten elements in a different order, specify the order option.
var array = require( '@stdlib/ndarray/array' );
function scale( value ) {
return value * 2.0;
}
var x = array( [ [ [ 1.0, 2.0 ] ], [ [ 3.0, 4.0 ] ], [ [ 5.0, 6.0 ] ] ] );
// returns <ndarray>
var opts = {
'order': 'column-major'
};
var y = flattenBy( x, opts, scale );
// returns <ndarray>[ 2.0, 6.0, 10.0, 4.0, 8.0, 12.0 ]By default, the output ndarray data type is inferred from the input ndarray. To return an ndarray with a different data type, specify the dtype option.
var array = require( '@stdlib/ndarray/array' );
var dtype = require( '@stdlib/ndarray/dtype' );
function scale( value ) {
return value * 2.0;
}
var x = array( [ [ [ 1.0, 2.0 ] ], [ [ 3.0, 4.0 ] ], [ [ 5.0, 6.0 ] ] ] );
// returns <ndarray>
var opts = {
'dtype': 'float32'
};
var y = flattenBy( x, opts, scale );
// returns <ndarray>[ 2.0, 4.0, 6.0, 8.0, 10.0, 12.0 ]
var dt = String( dtype( y ) );
// returns 'float32'To set the callback function execution context, provide a thisArg.
var array = require( '@stdlib/ndarray/array' );
function scale( value ) {
this.count += 1;
return value * 2.0;
}
var x = array( [ [ [ 1.0, 2.0 ] ], [ [ 3.0, 4.0 ] ], [ [ 5.0, 6.0 ] ] ] );
// returns <ndarray>
var ctx = {
'count': 0
};
var y = flattenBy( x, scale, ctx );
// returns <ndarray>[ 2.0, 4.0, 6.0, 8.0, 10.0, 12.0 ]
var count = ctx.count;
// returns 6-
The function always returns a copy of input ndarray data, even when an input ndarray already has the desired number of dimensions.
-
The callback function is provided the following arguments:
- value: current array element.
- indices: current array element indices.
- arr: the input ndarray.
-
The order in which array elements are traversed and passed to a provided callback function is not guaranteed to match the order of array elements in an ndarray view. Accordingly, a provided callback should avoid making assumptions regarding the order of provided elements.
var discreteUniform = require( '@stdlib/random/array/discrete-uniform' );
var array = require( '@stdlib/ndarray/array' );
var ndarray2array = require( '@stdlib/ndarray/to-array' );
var flattenBy = require( '@stdlib/ndarray/flatten-by' );
function scale( value ) {
return value * 2.0;
}
var xbuf = discreteUniform( 12, -100, 100, {
'dtype': 'generic'
});
var x = array( xbuf, {
'shape': [ 2, 2, 3 ],
'dtype': 'generic'
});
console.log( ndarray2array( x ) );
var y = flattenBy( x, scale );
console.log( ndarray2array( y ) );