function incrpcorr2( meanx, meany ) {
	var acc;
	if ( arguments.length ) {
		if ( !isNumber( meanx ) ) {
			throw new TypeError( format( 'invalid argument. First argument must be a number. Value: `%s`.', meanx ) );
		}
		if ( !isNumber( meany ) ) {
			throw new TypeError( format( 'invalid argument. Second argument must be a number. Value: `%s`.', meany ) );
		}
		acc = incrpcorr( meanx, meany );
	} else {
		acc = incrpcorr();
	}
	return accumulator;

	/**
	* If provided input values, the accumulator function returns an updated accumulated value. If not provided input values, the accumulator function returns the current accumulate value.
	*
	* @private
	* @param {number} [x] - new value
	* @param {number} [y] - new value
	* @returns {(number|null)} squared sample correlation coefficient or null
	*/
	function accumulator( x, y ) {
		var r;
		if ( arguments.length === 0 ) {
			r = acc();
			if ( r === null ) {
				return r;
			}
			return r * r;
		}
		r = acc( x, y );
		return r * r;
	}
}
Returns an accumulator function which incrementally computes a squared sample Pearson product-moment correlation coefficient.

@param {number} [meanx] - mean value
@param {number} [meany] - mean value
@throws {TypeError} first argument must be a number
@throws {TypeError} second argument must be a number
@returns {Function} accumulator function

@example
var accumulator = incrpcorr2();

var r2 = accumulator();
// returns null

r2 = accumulator( 2.0, 1.0 );
// returns 0.0

r2 = accumulator( -5.0, 3.14 );
// returns ~1.0

r2 = accumulator();
// returns ~1.0

@example
var accumulator = incrpcorr2( 2.0, -3.0 );