README.md

mskrange

Compute the range along one or more ndarray dimensions according to a mask.

The range is defined as the difference between the maximum and minimum values.

Usage

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

mskrange( x, mask[, options] )

Computes the range along one or more ndarray dimensions according to a mask.

var Float64Array = require( '@stdlib/array/float64' );
var Uint8Array = require( '@stdlib/array/uint8' );
var array = require( '@stdlib/ndarray/array' );

var x = array( new Float64Array( [ 1.0, 2.0, 3.0, 4.0, 5.0, 6.0 ] ), {
    'shape': [ 3, 2 ]
});
var mask = array( new Uint8Array( [ 0, 0, 1, 0, 0, 1 ] ), {
    'shape': [ 3, 2 ]
});

var y = mskrange( x, mask );
// returns <ndarray>[ 4.0 ]

The function has the following parameters:

• x: input ndarray. Must have a real-valued or "generic" data type.
• mask: mask ndarray. Must have a data type that can be interpreted as a mask.
• 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 Float64Array = require( '@stdlib/array/float64' );
var Uint8Array = require( '@stdlib/array/uint8' );
var array = require( '@stdlib/ndarray/array' );

var x = array( new Float64Array( [ 1.0, 2.0, 3.0, 4.0, 5.0, 6.0 ] ), {
    'shape': [ 3, 2 ],
    'order': 'row-major'
});
var mask = array( new Uint8Array( [ 0, 0, 1, 1, 0, 0 ] ), {
    'shape': [ 3, 2 ],
    'order': 'row-major'
});

var y = mskrange( x, mask, {
    'dims': [ 0 ]
});
// returns <ndarray>[ 4.0, 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 Float64Array = require( '@stdlib/array/float64' );
var Uint8Array = require( '@stdlib/array/uint8' );
var array = require( '@stdlib/ndarray/array' );

var x = array( new Float64Array( [ 1.0, 2.0, 3.0, 4.0, 5.0, 6.0 ] ), {
    'shape': [ 3, 2 ],
    'order': 'row-major'
});
var mask = array( new Uint8Array( [ 0, 0, 1, 1, 0, 0 ] ), {
    'shape': [ 3, 2 ],
    'order': 'row-major'
});

var y = mskrange( x, mask, {
    'dims': [ 0 ],
    'keepdims': true
});
// returns <ndarray>[ [ 4.0, 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 Float64Array = require( '@stdlib/array/float64' );
var Uint8Array = require( '@stdlib/array/uint8' );
var getDType = require( '@stdlib/ndarray/dtype' );
var array = require( '@stdlib/ndarray/array' );

var x = array( new Float64Array( [ 1.0, 2.0, 3.0 ] ), {
    'dtype': 'generic'
});
var mask = array( new Uint8Array( [ 0, 0, 0 ] ), {
    'dtype': 'uint8'
});

var y = mskrange( x, mask, {
    'dtype': 'float64'
});
// returns <ndarray>[ 2.0 ]

var dt = String( getDType( y ) );
// returns 'float64'

mskrange.assign( x, mask, out[, options] )

Computes the range along one or more ndarray dimensions according to a mask and assigns results to a provided output ndarray.

var Float64Array = require( '@stdlib/array/float64' );
var Uint8Array = require( '@stdlib/array/uint8' );
var array = require( '@stdlib/ndarray/array' );
var zeros = require( '@stdlib/ndarray/zeros' );

var x = array( new Float64Array( [ 1.0, 2.0, 3.0 ] ) );
var mask = array( new Uint8Array( [ 0, 0, 0 ] ) );
var y = zeros( [] );

var out = mskrange.assign( x, mask, y );
// returns <ndarray>[ 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.
• mask: mask ndarray. Must have a data type that can be interpreted as a mask.
• out: output ndarray.
• options: function options (optional).

The method 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 (or a promoted data type if the input data types differ). For the assign method, the output ndarray is allowed to have any supported output data type.

Examples

var uniform = require( '@stdlib/random/uniform' );
var bernoulli = require( '@stdlib/random/bernoulli' );
var getDType = require( '@stdlib/ndarray/dtype' );
var ndarray2array = require( '@stdlib/ndarray/to-array' );
var mskrange = require( '@stdlib/stats/mskrange' );

// Generate an array of random numbers:
var x = uniform( [ 5, 5 ], 0.0, 20.0 );
console.log( 'x:' );
console.log( ndarray2array( x ) );

// Generate a random mask:
var mask = bernoulli( [ 5, 5 ], 0.2, {
    'dtype': 'uint8'
});
console.log( 'mask:' );
console.log( ndarray2array( mask ) );

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

// Resolve the output array data type:
var dt = getDType( y );
console.log( 'Output dtype: %s', dt );

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