incrsumprod

Compute a sum of products incrementally.

The sum of products is defined as

Usage

var incrsumprod = require( '@stdlib/stats/incr/sumprod' );

incrsumprod()

Returns an accumulator function which incrementally computes a sum of products.

var accumulator = incrsumprod();

accumulator( [x, y] )

If provided input values x and y, the accumulator function returns an updated sum. If not provided input value x and y, the accumulator function returns the current sum.

var accumulator = incrsumprod();

var sum = accumulator( 2.0, 3.0 );
// returns 6.0

sum = accumulator( 1.0, -1.0 );
// returns 5.0

sum = accumulator( 3.0, 4.0 );
// returns 17.0

sum = accumulator();
// returns 17.0

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.
For long running accumulations or accumulations of large numbers, care should be taken to prevent overflow.

Examples

var randu = require( '@stdlib/random/base/randu' );
var incrsumprod = require( '@stdlib/stats/incr/sumprod' );

var accumulator;
var v1;
var v2;
var i;

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

// For each simulated datum, update the sum-product...
for ( i = 0; i < 100; i++ ) {
    v1 = randu() * 100.0;
    v2 = randu() * 100.0;
    accumulator( v1, v2 );
}
console.log( accumulator() );