# incrsumprod
> Compute a sum of products incrementally.
The sum of products is defined as
## Usage
```javascript
var incrsumprod = require( '@stdlib/stats/incr/sumprod' );
```
#### incrsumprod()
Returns an accumulator `function` which incrementally computes a sum of products.
```javascript
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.
```javascript
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
```javascript
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() );
```
