nditerSelectDimension

Create an iterator which iterates over each view along a specified dimension.

Usage

var nditerSelectDimension = require( '@stdlib/ndarray/iter/select-dimension' );

nditerSelectDimension( x, dim[, options] )

Returns an iterator which iterates over each view along a specified dimension.

var array = require( '@stdlib/ndarray/array' );
var ndarray2array = require( '@stdlib/ndarray/to-array' );

var x = array( [ [ [ 1, 2 ], [ 3, 4 ] ], [ [ 5, 6 ], [ 7, 8 ] ] ] );
// returns <ndarray>

var iter = nditerSelectDimension( x, 0 );

var v = iter.next().value;
// returns <ndarray>

var arr = ndarray2array( v );
// returns [ [ 1, 2 ], [ 3, 4 ] ]

v = iter.next().value;
// returns <ndarray>

arr = ndarray2array( v );
// returns [ [ 5, 6 ], [ 7, 8 ] ]

// ...

The function accepts the following options:

readonly: boolean indicating whether returned ndarray views should be read-only. In order to return writable ndarray views, the input ndarray must be writable. If the input ndarray is read-only, setting this option to false raises an exception. Default: true.
keepdim: boolean indicating whether returned ndarray views should include the selected dimension as a singleton dimension. If true, each returned view has the same number of dimensions as the input ndarray. Otherwise, each returned view has one fewer dimensions than the input ndarray. Default: false.

By default, the iterator returns ndarray views which are read-only. To return writable views, set the readonly option to false.

var array = require( '@stdlib/ndarray/array' );
var ndarray2array = require( '@stdlib/ndarray/to-array' );

var x = array( [ [ [ 1, 2 ], [ 3, 4 ] ], [ [ 5, 6 ], [ 7, 8 ] ] ] );
// returns <ndarray>

var iter = nditerSelectDimension( x, 0, {
    'readonly': false
});

var v = iter.next().value;
// returns <ndarray>

var arr = ndarray2array( v );
// returns [ [ 1, 2 ], [ 3, 4 ] ]

v.set( 0, 0, 10 );

arr = ndarray2array( v );
// returns [ [ 10, 2 ], [ 3, 4 ] ]

By default, the iterator returns ndarray views which omit the selected dimension, resulting in ndarray views having one fewer dimensions than the provided input ndarray. To include the selected dimension as a singleton dimension in the returned ndarray views, set the keepdim option to true.

var array = require( '@stdlib/ndarray/array' );
var ndarray2array = require( '@stdlib/ndarray/to-array' );

var x = array( [ [ [ 1, 2 ], [ 3, 4 ] ], [ [ 5, 6 ], [ 7, 8 ] ] ] );
// returns <ndarray>

var iter = nditerSelectDimension( x, 0, {
    'keepdim': true
});

var v = iter.next().value;
// returns <ndarray>

var arr = ndarray2array( v );
// returns [ [ [ 1, 2 ], [ 3, 4 ] ] ]

v = iter.next().value;
// returns <ndarray>

arr = ndarray2array( v );
// returns [ [ [ 5, 6 ], [ 7, 8 ] ] ]

// ...

The returned iterator protocol-compliant object has the following properties:

next: function which returns an iterator protocol-compliant object containing the next iterated value (if one exists) assigned to a value property and a done property having a boolean value indicating whether the iterator is finished.
return: function which closes an iterator and returns a single (optional) argument in an iterator protocol-compliant object.

Notes

If an environment supports Symbol.iterator, the returned iterator is iterable.
A returned iterator does not copy a provided ndarray. To ensure iterable reproducibility, copy the input ndarray before creating an iterator. Otherwise, any changes to the contents of input ndarray will be reflected in the returned iterator.
In environments supporting Symbol.iterator, the function explicitly does not invoke an ndarray's @@iterator method, regardless of whether this method is defined.
Including the selected dimension as a singleton dimension can be useful when wanting to ensure that returned views remain broadcast compatible with the input ndarray.

Examples

var array = require( '@stdlib/ndarray/array' );
var zeroTo = require( '@stdlib/array/base/zero-to' );
var ndarray2array = require( '@stdlib/ndarray/to-array' );
var nditerSelectDimension = require( '@stdlib/ndarray/iter/select-dimension' );

// Define an input array:
var x = array( zeroTo( 27 ), {
    'shape': [ 3, 3, 3 ]
});

// Create an iterator for iterating over matrices:
var it = nditerSelectDimension( x, 0 );

// Perform manual iteration...
var v;
while ( true ) {
    v = it.next();
    if ( v.done ) {
        break;
    }
    console.log( ndarray2array( v.value ) );
}