max

Compute the maximum value along one or more ndarray dimensions.

Usage

var max = require( '@stdlib/stats/max' );

max( x[, options] )

Computes the maximum value along one or more ndarray dimensions.

var ndarray = require( '@stdlib/ndarray/ctor' );

var xbuf = [ -1.0, 2.0, -3.0 ];
var x = new ndarray( 'generic', xbuf, [ xbuf.length ], [ 1 ], 0, 'row-major' );

var y = max( x );
// returns <ndarray>

var v = y.get();
// returns 2.0

The function has the following parameters:

• x: input ndarray. Must have a real-valued or "generic" data type.
• options: function options (optional).

The function accepts the following options:

• dims: list of dimensions over which to perform a reduction. If not provided, the function performs a reduction over all elements in a provided input ndarray.
• dtype: output ndarray data type. Must be a real-valued or "generic" data type.
• keepdims: boolean indicating whether the reduced dimensions should be included in the returned ndarray as singleton dimensions. Default: false.

By default, the function performs a reduction over all elements in a provided input ndarray. To perform a reduction over specific dimensions, provide a dims option.

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

var xbuf = [ -1.0, 2.0, -3.0, 4.0 ];
var x = new ndarray( 'generic', xbuf, [ 2, 2 ], [ 2, 1 ], 0, 'row-major' );

var y = max( x, {
    'dims': [ 0 ]
});
// returns <ndarray>

var v = ndarray2array( y );
// returns [ -1.0, 4.0 ]

y = max( x, {
    'dims': [ 1 ]
});
// returns <ndarray>

v = ndarray2array( y );
// returns [ 2.0, 4.0 ]

y = max( x, {
    'dims': [ 0, 1 ]
});
// returns <ndarray>

v = y.get();
// returns 4.0

By default, the function excludes reduced dimensions from the output ndarray. To include the reduced dimensions as singleton dimensions, set the keepdims option to true.

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

var xbuf = [ -1.0, 2.0, -3.0, 4.0 ];
var x = new ndarray( 'generic', xbuf, [ 2, 2 ], [ 2, 1 ], 0, 'row-major' );

var y = max( x, {
    'dims': [ 0 ],
    'keepdims': true
});
// returns <ndarray>

var v = ndarray2array( y );
// returns [ [ -1.0, 4.0 ] ]

y = max( x, {
    'dims': [ 1 ],
    'keepdims': true
});
// returns <ndarray>

v = ndarray2array( y );
// returns [ [ 2.0 ], [ 4.0 ] ]

y = max( x, {
    'dims': [ 0, 1 ],
    'keepdims': true
});
// returns <ndarray>

v = ndarray2array( y );
// returns [ [ 4.0 ] ]

By default, the function returns an ndarray having a data type determined by the function's output data type policy. To override the default behavior, set the dtype option.

var dtype = require( '@stdlib/ndarray/dtype' );
var ndarray = require( '@stdlib/ndarray/ctor' );

var xbuf = [ -1.0, 2.0, -3.0 ];
var x = new ndarray( 'generic', xbuf, [ xbuf.length ], [ 1 ], 0, 'row-major' );

var y = max( x, {
    'dtype': 'float64'
});
// returns <ndarray>

var dt = dtype( y );
// returns 'float64'

max.assign( x, out[, options] )

Computes the maximum value along one or more ndarray dimensions and assigns results to a provided output ndarray.

var ndarray = require( '@stdlib/ndarray/ctor' );

var xbuf = [ -1.0, 2.0, -3.0 ];
var x = new ndarray( 'generic', xbuf, [ xbuf.length ], [ 1 ], 0, 'row-major' );

var ybuf = [ 0.0 ];
var y = new ndarray( 'generic', ybuf, [], [ 0 ], 0, 'row-major' );

var out = max.assign( x, y );
// returns <ndarray>

var v = out.get();
// returns 2.0

var bool = ( out === y );
// returns true

The method has the following parameters:

• x: input ndarray. Must have a real-valued or generic data type.
• out: output ndarray.
• options: function options (optional).

The function accepts the following options:

• dims: list of dimensions over which to perform a reduction. If not provided, the function performs a reduction over all elements in a provided input ndarray.

Notes

• Setting the keepdims option to true can be useful when wanting to ensure that the output ndarray is broadcast-compatible with ndarrays having the same shape as the input ndarray.
• The output data type policy only applies to the main function and specifies that, by default, the function must return an ndarray having the same data type as the input ndarray. For the assign method, the output ndarray is allowed to have any data type.

Examples

var discreteUniform = require( '@stdlib/random/array/discrete-uniform' );
var dtype = require( '@stdlib/ndarray/dtype' );
var ndarray2array = require( '@stdlib/ndarray/to-array' );
var ndarray = require( '@stdlib/ndarray/ctor' );
var max = require( '@stdlib/stats/max' );

// Generate an array of random numbers:
var xbuf = discreteUniform( 25, 0, 20, {
    'dtype': 'generic'
});

// Wrap in an ndarray:
var x = new ndarray( 'generic', xbuf, [ 5, 5 ], [ 5, 1 ], 0, 'row-major' );
console.log( ndarray2array( x ) );

// Perform a reduction:
var y = max( x, {
    'dims': [ 0 ]
});

// Resolve the output array data type:
var dt = dtype( y );
console.log( dt );

// Print the results:
console.log( ndarray2array( y ) );