function nanvariancetk( N, correction, x, strideX, offsetX ) {
	var S2;
	var ix;
	var nc;
	var o;
	var S;
	var v;
	var n;
	var i;

	if ( N <= 0 ) {
		return NaN;
	}
	o = arraylike2object( x );
	if ( o.accessorProtocol ) {
		return accessors( N, correction, o, strideX, offsetX );
	}
	if ( N === 1 || strideX === 0 ) {
		v = x[ offsetX ];
		if ( v === v && N-correction > 0.0 ) {
			return 0.0;
		}
		return NaN;
	}
	ix = offsetX;
	S2 = 0.0;
	S = 0.0;
	n = 0;
	for ( i = 0; i < N; i++ ) {
		v = x[ ix ];
		if ( v === v ) {
			S2 += v * v;
			S += v;
			n += 1;
		}
		ix += strideX;
	}
	nc = n - correction;
	if ( nc <= 0.0 ) {
		return NaN;
	}
	return (S2 - ((S/n)*S)) / nc;
}
Computes the variance of a strided array ignoring `NaN` values and using a one-pass textbook 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
@param {NonNegativeInteger} offsetX - starting index
@returns {number} variance

@example
var x = [ 2.0, 1.0, 2.0, -2.0, -2.0, 2.0, 3.0, 4.0, NaN, NaN ];

var v = nanvariancetk( 5, 1, x, 2, 1 );
// returns 6.25