Mean

Triangular distribution expected value.

The mean for a triangular random variable is

where a is the lower limit, b is the upper limit and c is the mode.

Usage

var mean = require( '@stdlib/stats/base/dists/triangular/mean' );

mean( a, b, c )

Returns the expected value of a triangular distribution with parameters a (minimum support), b (maximum support), and c (mode).

var v = mean( 0.0, 1.0, 0.8 );
// returns ~0.6

v = mean( 4.0, 12.0, 5.0 );
// returns 7.0

v = mean( 2.0, 8.0, 5.0 );
// returns 5.0

If provided NaN as any argument, the function returns NaN.

var v = mean( NaN, 4.0, 2.0 );
// returns NaN

v = mean( 0.0, NaN, 2.0 );
// returns NaN

v = mean( 0.0, 4.0, NaN );
// returns NaN

If provided parameters not satisfying a <= c <= b, the function returns NaN.

var y = mean( 1.0, 0.0, 1.5 );
// returns NaN

y = mean( 0.0, 1.0, -1.0 );
// returns NaN

y = mean( 0.0, -1.0, 0.5 );
// returns NaN

Examples

var randu = require( '@stdlib/random/base/randu' );
var mean = require( '@stdlib/stats/base/dists/triangular/mean' );

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

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

C APIs

Usage

#include "stdlib/stats/base/dists/triangular/mean.h"

stdlib_base_dists_triangular_mean( a, b, c )

Returns the expected value of a triangular distribution.

double out = stdlib_base_dists_triangular_mean( 0.0, 1.0, 0.5 );
// returns ~0.333

The function accepts the following arguments:

a: [in] double minimum support.
b: [in] double maximum support.
c: [in] double mode.

double stdlib_base_dists_triangular_mean( const double a, const double b, const double c );

Examples

#include "stdlib/stats/base/dists/triangular/mean.h"
#include <stdlib.h>
#include <stdio.h>

static double random_uniform( const double min, const double max ) {
    double v = (double)rand() / ( (double)RAND_MAX + 1.0 );
    return min + ( v*(max-min) );
}

int main( void ) {
    double a;
    double b;
    double c;
    double y;
    int i;

    for ( i = 0; i < 25; i++ ) {
        a = random_uniform( 0.0, 10.0 );
        b = random_uniform( a, 10.0 + a );
        c = random_uniform( a, b ); // mode between a and b
        y = stdlib_base_dists_triangular_mean( a, b, c );
        printf( "a: %lf, b: %lf, c: %lf, E(X;a,b,c): %lf\n", a, b, c, y );
    }
}