Compute the mid-range along one or more ndarray dimensions according to a callback function.
The mid-range, or mid-extreme, is the arithmetic mean of the maximum and minimum values in a data set. The measure is the midpoint of the range and a measure of central tendency.
var midrangeBy = require( '@stdlib/stats/midrange-by' );Computes the mid-range along one or more ndarray dimensions according to a callback function.
var array = require( '@stdlib/ndarray/array' );
var x = array( [ -1.0, 2.0, -3.0 ] );
function clbk( v ) {
return v * 2.0;
}
var y = midrangeBy( x, clbk );
// returns <ndarray>[ -1.0 ]The function has the following parameters:
- x: input ndarray.
- options: function options (optional).
- clbk: callback function.
- thisArg: callback function execution context (optional).
The invoked callback is provided three arguments:
- value: current array element.
- index: current array element index.
- array: input ndarray.
To set the callback execution context, provide a thisArg.
var array = require( '@stdlib/ndarray/array' );
var x = array( [ -1.0, 2.0, -3.0 ] );
function clbk( v ) {
this.count += 1;
return v * 2.0;
}
var ctx = {
'count': 0
};
var y = midrangeBy( x, clbk, ctx );
// returns <ndarray>[ -1.0 ]
var count = ctx.count;
// returns 3The 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 array = require( '@stdlib/ndarray/array' );
function clbk( v ) {
return v * 100.0;
}
var x = array( [ -1.0, 2.0, -3.0, 4.0 ], {
'shape': [ 2, 2 ],
'order': 'row-major'
});
// returns <ndarray>[ [ -1.0, 2.0 ], [ -3.0, 4.0 ] ]
var opts = {
'dims': [ 0 ]
};
var y = midrangeBy( x, opts, clbk );
// returns <ndarray>[ -200.0, 300.0 ]
opts = {
'dims': [ 1 ]
};
y = midrangeBy( x, opts, clbk );
// returns <ndarray>[ 50.0, 50.0 ]
opts = {
'dims': [ 0, 1 ]
};
y = midrangeBy( x, opts, clbk );
// returns <ndarray>[ 50.0 ]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 array = require( '@stdlib/ndarray/array' );
function clbk( v ) {
return v * 100.0;
}
var x = array( [ -1.0, 2.0, -3.0, 4.0 ], {
'shape': [ 2, 2 ],
'order': 'row-major'
});
// returns <ndarray>[ [ -1.0, 2.0 ], [ -3.0, 4.0 ] ]
var opts = {
'dims': [ 0 ],
'keepdims': true
};
var y = midrangeBy( x, opts, clbk );
// returns <ndarray>[ [ -200.0, 300.0 ] ]
opts = {
'dims': [ 1 ],
'keepdims': true
};
y = midrangeBy( x, opts, clbk );
// returns <ndarray>[ [ 50.0 ], [ 50.0 ] ]
opts = {
'dims': [ 0, 1 ],
'keepdims': true
};
y = midrangeBy( x, opts, clbk );
// returns <ndarray>[ [ 50.0 ] ]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 getDType = require( '@stdlib/ndarray/dtype' );
var array = require( '@stdlib/ndarray/array' );
function clbk( v ) {
return v * 100.0;
}
var x = array( [ -1.0, 2.0, -3.0 ], {
'dtype': 'generic'
});
var opts = {
'dtype': 'float64'
};
var y = midrangeBy( x, opts, clbk );
// returns <ndarray>
var dt = String( getDType( y ) );
// returns 'float64'Computes the mid-range along one or more ndarray dimensions according to a callback function and assigns results to a provided output ndarray.
var array = require( '@stdlib/ndarray/array' );
var zeros = require( '@stdlib/ndarray/zeros' );
function clbk( v ) {
return v * 100.0;
}
var x = array( [ -1.0, 2.0, -3.0 ] );
var y = zeros( [] );
var out = midrangeBy.assign( x, y, clbk );
// returns <ndarray>[ -50.0 ]
var bool = ( out === y );
// returns trueThe method has the following parameters:
- x: input ndarray.
- out: output ndarray.
- options: function options (optional).
- clbk: callback function.
- thisArg: callback execution context (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.
- A provided callback function should return a numeric value.
- If a provided callback function does not return any value (or equivalently, explicitly returns
undefined), the value is ignored. - Setting the
keepdimsoption totruecan 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 a real-valued or "generic" data type. For the
assignmethod, the output ndarray is allowed to have any supported output data type.
var filledarrayBy = require( '@stdlib/array/filled-by' );
var discreteUniform = require( '@stdlib/random/base/discrete-uniform' );
var getDType = require( '@stdlib/ndarray/dtype' );
var ndarray2array = require( '@stdlib/ndarray/to-array' );
var ndarray = require( '@stdlib/ndarray/ctor' );
var midrangeBy = require( '@stdlib/stats/midrange-by' );
// Define a function for generating an object having a random value:
function random() {
return {
'value': discreteUniform( 0, 20 )
};
}
// Generate an array of random objects:
var xbuf = filledarrayBy( 25, 'generic', random );
// Wrap in an ndarray:
var x = new ndarray( 'generic', xbuf, [ 5, 5 ], [ 5, 1 ], 0, 'row-major' );
console.log( ndarray2array( x ) );
// Define an accessor function:
function accessor( v ) {
return v.value * 100;
}
// Perform a reduction:
var opts = {
'dims': [ 0 ]
};
var y = midrangeBy( x, opts, accessor );
// Resolve the output array data type:
var dt = String( getDType( y ) );
console.log( dt );
// Print the results:
console.log( ndarray2array( y ) );