dnannsum
Calculate the sum of double-precision floating-point strided array elements, ignoring
NaN
values.
Usage
var dnannsum = require( '@stdlib/blas/ext/base/dnannsum' );
dnannsum( N, x, strideX, out, strideOut )
Computes the sum of double-precision floating-point strided array elements, ignoring NaN
values.
var Float64Array = require( '@stdlib/array/float64' );
var x = new Float64Array( [ 1.0, -2.0, NaN, 2.0 ] );
var out = new Float64Array( 2 );
var v = dnannsum( x.length, x, 1, out, 1 );
// returns <Float64Array>[ 1.0, 3 ]
The function has the following parameters:
- N: number of indexed elements.
- x: input
Float64Array
. - strideX: index increment for
x
. - out: output
Float64Array
whose first element is the sum and whose second element is the number of non-NaN elements. - strideOut: index increment for
out
.
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,
var Float64Array = require( '@stdlib/array/float64' );
var x = new Float64Array( [ 1.0, 2.0, NaN, -7.0, NaN, 3.0, 4.0, 2.0 ] );
var out = new Float64Array( 2 );
var v = dnannsum( 4, x, 2, out, 1 );
// returns <Float64Array>[ 5.0, 2 ]
Note that indexing is relative to the first index. To introduce an offset, use typed array
views.
var Float64Array = require( '@stdlib/array/float64' );
var x0 = new Float64Array( [ 2.0, 1.0, NaN, -2.0, -2.0, 2.0, 3.0, 4.0 ] );
var x1 = new Float64Array( x0.buffer, x0.BYTES_PER_ELEMENT*1 ); // start at 2nd element
var out0 = new Float64Array( 4 );
var out1 = new Float64Array( out0.buffer, out0.BYTES_PER_ELEMENT*2 ); // start at 3rd element
var v = dnannsum( 4, x1, 2, out1, 1 );
// returns <Float64Array>[ 5.0, 4 ]
dnannsum.ndarray( N, x, strideX, offsetX, out, strideOut, offsetOut )
Computes the sum of double-precision floating-point strided array elements, ignoring NaN
values and using alternative indexing semantics.
var Float64Array = require( '@stdlib/array/float64' );
var x = new Float64Array( [ 1.0, -2.0, NaN, 2.0 ] );
var out = new Float64Array( 2 );
var v = dnannsum.ndarray( x.length, x, 1, 0, out, 1, 0 );
// returns <Float64Array>[ 1.0, 3 ]
The function has the following additional parameters:
- offsetX: starting index for
x
. - offsetOut: starting index for
out
.
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 the strided array starting from the second value
var Float64Array = require( '@stdlib/array/float64' );
var x = new Float64Array( [ 2.0, 1.0, NaN, -2.0, -2.0, 2.0, 3.0, 4.0 ] );
var out = new Float64Array( 4 );
var v = dnannsum.ndarray( 4, x, 2, 1, out, 2, 1 );
// returns <Float64Array>[ 0.0, 5.0, 0.0, 4 ]
Notes
- If
N <= 0
, both functions return a sum equal to0.0
.
Examples
var bernoulli = require( '@stdlib/random/base/bernoulli' );
var discreteUniform = require( '@stdlib/random/base/discrete-uniform' );
var filledarrayBy = require( '@stdlib/array/filled-by' );
var Float64Array = require( '@stdlib/array/float64' );
var dnannsum = require( '@stdlib/blas/ext/base/dnannsum' );
function clbk() {
if ( bernoulli( 0.7 ) > 0 ) {
return discreteUniform( 0, 100 );
}
return NaN;
}
var x = filledarrayBy( 10, 'float64', clbk );
console.log( x );
var out = new Float64Array( 2 );
dnannsum( x.length, x, 1, out, 1 );
console.log( out );