Mean

Discrete uniform distribution expected value.

The expected value for a discrete uniform random variable is

double-struck upper E left-bracket upper X right-bracket equals 0.5 dot left-parenthesis a plus b right-parenthesis

where a is the minimum support and b the maximum support of the distribution.

Usage

var mean = require( '@stdlib/math/base/dists/discrete-uniform/mean' );

mean( a, b )

Returns the expected value of a discrete uniform distribution with parameters a (minimum support) and b (maximum support).

var v = mean( 0, 1 );
// returns 0.5

v = mean( 4, 12 );
// returns 8.0

v = mean( 2, 8 );
// returns 5.0

If a or b is not an integer value, the function returns NaN.

var v = mean( 0.1, 2 );
// returns NaN

v = mean( 0, 2.2 );
// returns NaN

v = mean( NaN, 2 );
// returns NaN

v = mean( 2, NaN );
// returns NaN

If provided a > b, the function returns NaN.

var y = mean( 3, 2 );
// returns NaN

y = mean( -1, -2 );
// returns NaN

Examples

var randu = require( '@stdlib/random/base/randu' );
var round = require( '@stdlib/math/base/special/round' );
var mean = require( '@stdlib/math/base/dists/discrete-uniform/mean' );

var a;
var b;
var v;
var i;

for ( i = 0; i < 10; i++ ) {
    a = round( randu()*10.0 );
    b = round( ( randu()*10.0 ) + a );
    v = mean( a, b );
    console.log( 'a: %d, b: %d, E(X;a,b): %d', a.toFixed( 4 ), b.toFixed( 4 ), v.toFixed( 4 ) );
}