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README.md

midrange

Calculate the mid-range of a strided array.

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.

Usage

var midrange = require( '@stdlib/stats/strided/midrange' );

midrange( N, x, strideX )

Computes the mid-range of a strided array.

var x = [ 1.0, -2.0, 2.0 ];

var v = midrange( x.length, x, 1 );
// returns 0.0

The function has the following parameters:

  • N: number of indexed elements.
  • x: input Array or typed array.
  • strideX: stride length for x.

The N and stride parameters determine which elements in the strided array are accessed at runtime. For example, to compute the mid-range of every other element in x,

var x = [ 1.0, 2.0, 2.0, -7.0, -2.0, 3.0, 4.0, 2.0 ];

var v = midrange( 4, x, 2 );
// returns 1.0

Note that indexing is relative to the first index. To introduce an offset, use typed array views.

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

var x0 = new Float64Array( [ 2.0, 1.0, 2.0, -2.0, -2.0, 2.0, 3.0, 4.0 ] );
var x1 = new Float64Array( x0.buffer, x0.BYTES_PER_ELEMENT*1 ); // start at 2nd element

var v = midrange( 4, x1, 2 );
// returns 1.0

midrange.ndarray( N, x, strideX, offsetX )

Computes the mid-range of a strided array using alternative indexing semantics.

var x = [ 1.0, -2.0, 2.0 ];

var v = midrange.ndarray( x.length, x, 1, 0 );
// returns 0.0

The function has the following additional parameters:

  • offsetX: starting index for x.

While typed array views mandate a view offset based on the underlying buffer, the offset parameter supports indexing semantics based on a starting index. For example, to calculate the mid-range for every other element in x starting from the second element

var x = [ 2.0, 1.0, 2.0, -2.0, -2.0, 2.0, 3.0, 4.0 ];

var v = midrange.ndarray( 4, x, 2, 1 );
// returns 1.0

Notes

  • If N <= 0, both functions return NaN.
  • Depending on the environment, the typed versions (dmidrange, smidrange, etc.) are likely to be significantly more performant.
  • Both functions support array-like objects having getter and setter accessors for array element access (e.g., @stdlib/array/base/accessor).

Examples

var discreteUniform = require( '@stdlib/random/array/discrete-uniform' );
var midrange = require( '@stdlib/stats/strided/midrange' );

var x = discreteUniform( 10, -50, 50, {
    'dtype': 'float64'
});
console.log( x );

var v = midrange( x.length, x, 1 );
console.log( v );