Return a read-only view of the first element (or subarray) along one or more
ndarraydimensions.
var first = require( '@stdlib/ndarray/first' );Returns a read-only view of the first element (or subarray) along one or more ndarray dimensions.
var array = require( '@stdlib/ndarray/array' );
var x = array( [ [ 1.0, 2.0 ], [ 3.0, 4.0 ] ] );
// returns <ndarray>[ [ 1.0, 2.0 ], [ 3.0, 4.0 ] ]
var v = first( x );
// returns <ndarray>[ 1.0 ]The function accepts the following arguments:
- x: input
ndarray. - options: function options.
The function accepts the following options:
- dims: list of dimensions over which to perform the operation. If a dimension index is provided as an integer less than zero, the dimension index is resolved relative to the last dimension, with the last dimension corresponding to the value
-1. By default, the function performs the operation over all dimensions.
To resolve the first element (or subarray) along one or more specified dimensions, provide a dims option:
var array = require( '@stdlib/ndarray/array' );
var x = array( [ [ 1.0, 2.0 ], [ 3.0, 4.0 ] ] );
// returns <ndarray>[ [ 1.0, 2.0 ], [ 3.0, 4.0 ] ]
// First column:
var v = first( x, {
'dims': [ -1 ]
});
// returns <ndarray>[ 1.0, 3.0 ]
// First row:
v = first( x, {
'dims': [ -2 ]
});
// returns <ndarray>[ 1.0, 2.0 ]- The function always returns a read-only view. To convert a returned view to a writable
ndarray, copy the contents to a newndarray(e.g., via@stdlib/ndarray/copy). - If provided an empty
dimsarray, the function returns a read-only view of the inputndarray.
var uniform = require( '@stdlib/random/uniform' );
var ndarray2array = require( '@stdlib/ndarray/to-array' );
var first = require( '@stdlib/ndarray/first' );
var x = uniform( [ 3, 3, 3 ], -10.0, 10.0 );
console.log( ndarray2array( x ) );
// First scalar element:
var v = first( x );
console.log( v.get() );
// First columns along the innermost dimension:
v = first( x, {
'dims': [ -1 ]
});
console.log( ndarray2array( v ) );
// First matrix along the outermost dimension:
v = first( x, {
'dims': [ 0 ]
});
console.log( ndarray2array( v ) );