nditerStacks

Create an iterator which iterates over each subarray in a stack of subarrays according to a list of specified stack dimensions.

Usage

var nditerStacks = require( '@stdlib/ndarray/iter/stacks' );

nditerStacks( x, dims[, options] )

Returns an iterator which iterates over each subarray in a stack of subarrays according to a list of specified stack dimensions.

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 = nditerStacks( x, [ 1, 2 ] );

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.

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 = nditerStacks( x, [ 1, 2 ], {
    '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 ] ]

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

  • The input ndarray must have at least dims.length+1 dimensions.
  • The list of provided index dimensions must be unique and resolve to index dimensions sorted in ascending order (i.e., the function does not allow rearranging ndarray dimensions by specifying an arbitrary index order).
  • 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.

Examples

var array = require( '@stdlib/ndarray/array' );
var zeroTo = require( '@stdlib/array/base/zero-to' );
var ndarray2array = require( '@stdlib/ndarray/to-array' );
var nditerStacks = require( '@stdlib/ndarray/iter/stacks' );

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

// Create an iterator for iterating over matrices:
var it = nditerStacks( x, [ 1, 2 ] );

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

// Create an iterator for iterating over matrices:
it = nditerStacks( x, [ 0, 2 ] );

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

// Create an iterator for iterating over matrices:
it = nditerStacks( x, [ 0, 1 ] );

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

See Also

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