function nanmskrange( N, x, strideX, mask, strideMask ) {
	var ix = stride2offset( N, strideX );
	var im = stride2offset( N, strideMask);
	return ndarray( N, x, strideX, ix, mask, strideMask, im );
}
Computes the range of a strided array according to a mask, ignoring `NaN` values.

@param {PositiveInteger} N - number of indexed elements
@param {NumericArray} x - input array
@param {integer} strideX - `x` stride length
@param {NumericArray} mask - mask array
@param {integer} strideMask - `mask` stride length
@returns {number} range

@example
var x = [ 1.0, -2.0, 4.0, 2.0, NaN ];
var mask = [ 0, 0, 1, 0, 0 ];

var v = nanmskrange( x.length, x, 1, mask, 1 );
// returns 4.0