var a[4] = {1, 4, 3, 5};
printf("n%f", Median(a, 4));
printf("n%f", Percentile(a, 4, 50));

# output
4.500000
4.500000

x <- c(1,3,4,5)
median(x)
[1] 3.5

var percentile(vars data, int length, var percent)
{
	int* ids = sortIdx(data, length);
	var pos = (length-1)*percent/100;
	var below = data[ids[min(length-1, (int)pos)]];
	if(pos == round(pos))
		return below;
	var above = data[ids[min(length-1, (int)pos+1)]];
	return (below+above)/2;
}