function nanvariancewd( N, correction, x, strideX ) {
	return ndarray( N, correction, x, strideX, stride2offset( N, strideX ) );
}
Computes the variance of a strided array ignoring `NaN` values and using Welford's algorithm.

@param {PositiveInteger} N - number of indexed elements
@param {number} correction - degrees of freedom adjustment
@param {NumericArray} x - input array
@param {integer} strideX - stride length
@returns {number} variance

@example
var x = [ 1.0, -2.0, NaN, 2.0 ];

var v = nanvariancewd( x.length, 1, x, 1 );
// returns ~4.3333