time-to-botec/js/node_modules/@stdlib/stats/incr/sum/README.md

incrsum

Compute a sum incrementally.

The sum is defined as

Usage

var incrsum = require( '@stdlib/stats/incr/sum' );

incrsum()

Returns an accumulator function which incrementally computes a sum.

var accumulator = incrsum();

accumulator( [x] )

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

var accumulator = incrsum();

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

sum = accumulator( 1.0 );
// returns 3.0

sum = accumulator( 3.0 );
// returns 6.0

sum = accumulator();
// returns 6.0

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 incrsum = require( '@stdlib/stats/incr/sum' );

var accumulator;
var v;
var i;

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

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

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References

• Klein, Andreas. 2005. "A Generalized Kahan-Babuška-Summation-Algorithm." Computing 76 (3): 279–93. doi:10.1007/s00607-005-0139-x.