Compute an arithmetic mean incrementally.

The arithmetic mean is defined as

mu equals StartFraction 1 Over n EndFraction sigma-summation Underscript i equals 0 Overscript n minus 1 Endscripts x Subscript i


var incrmean = require( '@stdlib/stats/incr/mean' );


Returns an accumulator function which incrementally computes an arithmetic mean.

var accumulator = incrmean();

accumulator( [x] )

If provided an input value x, the accumulator function returns an updated mean. If not provided an input value x, the accumulator function returns the current mean.

var accumulator = incrmean();

var mu = accumulator( 2.0 );
// returns 2.0

mu = accumulator( 1.0 );
// returns 1.5

mu = accumulator( 3.0 );
// returns 2.0

mu = accumulator();
// returns 2.0


  • Input values are not type checked. If provided NaN or a value which, when used in computations, results in NaN, the accumulated value is NaN for all future invocations. If non-numeric inputs are possible, you are advised to type check and handle accordingly before passing the value to the accumulator function.


var randu = require( '@stdlib/random/base/randu' );
var incrmean = require( '@stdlib/stats/incr/mean' );

var accumulator;
var v;
var i;

// Initialize an accumulator:
accumulator = incrmean();

// For each simulated datum, update the mean...
for ( i = 0; i < 100; i++ ) {
    v = randu() * 100.0;
    accumulator( v );
console.log( accumulator() );
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