static Sample<Double> ofDouble(
		final double x1,
		final double x2,
		final double y
	) {
		return new DoubleSample(x1, x2, y);
	}
Create a new sample point from the given argument and sample result. It
represents the function arguments with the function value:
{@code f: (x1, x2) -> y}

@param x1 the first argument
@param x2 the second argument
@param y the sample point result
@return a new sample point
jenetics.prog/src/main/java/io/jenetics/prog/regression/Sample.java