Calculate the sum of single-precision floating-point strided array elements, ignoring
NaNvalues.
var snansum = require( '@stdlib/blas/ext/base/snansum' );Computes the sum of single-precision floating-point strided array elements, ignoring NaN values.
var Float32Array = require( '@stdlib/array/float32' );
var x = new Float32Array( [ 1.0, -2.0, NaN, 2.0 ] );
var N = x.length;
var v = snansum( N, x, 1 );
// returns 1.0The function accepts the following parameters:
- N: number of indexed elements.
- x: input
Float32Array. - stride: index increment for
x.
The N and stride parameters determine which elements in x are accessed at runtime. For example, to compute the sum of every other element in x,
var Float32Array = require( '@stdlib/array/float32' );
var floor = require( '@stdlib/math/base/special/floor' );
var x = new Float32Array( [ 1.0, 2.0, NaN, -7.0, NaN, 3.0, 4.0, 2.0 ] );
var N = floor( x.length / 2 );
var v = snansum( N, x, 2 );
// returns 5.0Note that indexing is relative to the first index. To introduce an offset, use typed array views.
var Float32Array = require( '@stdlib/array/float32' );
var floor = require( '@stdlib/math/base/special/floor' );
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 N = floor( x0.length / 2 );
var v = snansum( N, x1, 2 );
// returns 5.0Computes the sum of single-precision floating-point strided array elements, ignoring NaN values and using alternative indexing semantics.
var Float32Array = require( '@stdlib/array/float32' );
var x = new Float32Array( [ 1.0, -2.0, NaN, 2.0 ] );
var N = x.length;
var v = snansum.ndarray( N, x, 1, 0 );
// returns 1.0The function accepts the following additional parameters:
- offset: starting index for
x.
While 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 x starting from the second value
var Float32Array = require( '@stdlib/array/float32' );
var floor = require( '@stdlib/math/base/special/floor' );
var x = new Float32Array( [ 2.0, 1.0, NaN, -2.0, -2.0, 2.0, 3.0, 4.0 ] );
var N = floor( x.length / 2 );
var v = snansum.ndarray( N, x, 2, 1 );
// returns 5.0- If
N <= 0, both functions return0.0.
var randu = require( '@stdlib/random/base/randu' );
var round = require( '@stdlib/math/base/special/round' );
var Float32Array = require( '@stdlib/array/float32' );
var snansum = require( '@stdlib/blas/ext/base/snansum' );
var x;
var i;
x = new Float32Array( 10 );
for ( i = 0; i < x.length; i++ ) {
if ( randu() < 0.2 ) {
x[ i ] = NaN;
} else {
x[ i ] = round( randu()*100.0 );
}
}
console.log( x );
var v = snansum( x.length, x, 1 );
console.log( v );- Neumaier, Arnold. 1974. "Rounding Error Analysis of Some Methods for Summing Finite Sums." Zeitschrift Für Angewandte Mathematik Und Mechanik 54 (1): 39–51. doi:10.1002/zamm.19740540106.