incrstdev

Compute a corrected sample standard deviation incrementally.

Usage

var incrstdev = require( '@stdlib/math/stats/incr/stdev' );

incrstdev()

Returns an accumulator function which incrementally computes a corrected sample standard deviation.

var accumulator = incrstdev();

accumulator( [x] )

If provided an input value x, the accumulator function returns an updated corrected sample standard deviation. If not provided an input value x, the accumulator function returns the current corrected sample standard deviation.

var s = accumulator( 2.0 );
// returns 0.0

s = accumulator( 1.0 ); // => sqrt(((2-1.5)^2+(1-1.5)^2) / (2-1))
// returns ~0.7071

s = accumulator( 3.0 ); // => sqrt(((2-2)^2+(1-2)^2+(3-2)^2) / (3-1))
// returns 1.0

s = accumulator();
// returns 1.0

Notes

  • 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.

Examples

var randu = require( '@stdlib/random/base/randu' );
var incrstdev = require( '@stdlib/math/stats/incr/stdev' );

var accumulator;
var v;
var i;

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

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