# sdsnansum
> Calculate the sum of single-precision floating-point strided array elements, ignoring `NaN` values and using extended accumulation.
## Usage
```javascript
var sdsnansum = require( '@stdlib/blas/ext/base/sdsnansum' );
```
#### sdsnansum( N, x, stride )
Computes the sum of single-precision floating-point strided array elements, ignoring `NaN` values and using extended accumulation.
```javascript
var Float32Array = require( '@stdlib/array/float32' );
var x = new Float32Array( [ 1.0, -2.0, NaN, 2.0 ] );
var v = sdsnansum( 4, x, 1 );
// returns 1.0
```
The function has the following parameters:
- **N**: number of indexed elements.
- **x**: input [`Float32Array`][@stdlib/array/float32].
- **stride**: index increment for the strided array.
The `N` and `stride` parameters determine which elements in the strided array are accessed at runtime. For example, to compute the sum of every other element in the strided array,
```javascript
var Float32Array = require( '@stdlib/array/float32' );
var x = new Float32Array( [ 1.0, 2.0, NaN, -7.0, NaN, 3.0, 4.0, 2.0 ] );
var v = sdsnansum( 4, x, 2 );
// returns 5.0
```
Note that indexing is relative to the first index. To introduce an offset, use [`typed array`][mdn-typed-array] views.
```javascript
var Float32Array = require( '@stdlib/array/float32' );
var x0 = new Float32Array( [ 2.0, 1.0, NaN, -2.0, -2.0, 2.0, 3.0, 4.0 ] );
var x1 = new Float32Array( x0.buffer, x0.BYTES_PER_ELEMENT*1 ); // start at 2nd element
var v = sdsnansum( 4, x1, 2 );
// returns 5.0
```
#### sdsnansum.ndarray( N, x, stride, offset )
Computes the sum of single-precision floating-point strided array elements, ignoring `NaN` values and using extended accumulation and alternative indexing semantics.
```javascript
var Float32Array = require( '@stdlib/array/float32' );
var x = new Float32Array( [ 1.0, -2.0, NaN, 2.0 ] );
var N = x.length;
var v = sdsnansum.ndarray( N, x, 1, 0 );
// returns 1.0
```
The function has the following additional parameters:
- **offset**: starting index for the strided array.
While [`typed array`][mdn-typed-array] views mandate a view offset based on the underlying `buffer`, the `offset` parameter supports indexing semantics based on a starting index. For example, to calculate the sum of every other value in the strided array starting from the second value
```javascript
var Float32Array = require( '@stdlib/array/float32' );
var x = new Float32Array( [ 2.0, 1.0, NaN, -2.0, -2.0, 2.0, 3.0, 4.0 ] );
var v = sdsnansum.ndarray( 4, x, 2, 1 );
// returns 5.0
```
## Notes
- If `N <= 0`, both functions return `0.0`.
- Accumulated intermediate values are stored as double-precision floating-point numbers.
## Examples
```javascript
var discreteUniform = require( '@stdlib/random/base/discrete-uniform' );
var bernoulli = require( '@stdlib/random/base/bernoulli' );
var filledarrayBy = require( '@stdlib/array/filled-by' );
var sdsnansum = require( '@stdlib/blas/ext/base/sdsnansum' );
function randOrNan() {
if ( bernoulli() < 0.2 ) {
return NaN;
}
return discreteUniform( 0, 100 );
}
var x = filledarrayBy( 10, 'float32', randOrNan );
console.log( x );
var v = sdsnansum( x.length, x, 1 );
console.log( v );
```
[@stdlib/array/float32]: https://www.npmjs.com/package/@stdlib/array-float32
[mdn-typed-array]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray
[@stdlib/blas/ext/base/dsnansum]: https://github.com/stdlib-js/blas/tree/main/ext/base/dsnansum
[@stdlib/blas/ext/base/dnansum]: https://github.com/stdlib-js/blas/tree/main/ext/base/dnansum
[@stdlib/blas/ext/base/gnansum]: https://github.com/stdlib-js/blas/tree/main/ext/base/gnansum
[@stdlib/blas/ext/base/sdssum]: https://github.com/stdlib-js/blas/tree/main/ext/base/sdssum
[@stdlib/blas/ext/base/snansum]: https://github.com/stdlib-js/blas/tree/main/ext/base/snansum