data data.6
	read {y 1}
	define DIM (dimen(y))
	set dimen(xsum)=128
	set dimen(xsum2)=128
	set x=1,$DIM
	define N 0

	do i=1,$DIM,128{
		set yl=y if(x>=$i&&x<$i+128)
		set xsum=xsum+yl
		set xsum2=xsum2+yl**2
		define N ($N+1)
	}
 	
	set x=1,128
	set xave=xsum/$N
	set err=sqrt((xsum2/$N - xave**2)/$N)
	limits 0 130  xave
	box
	connect x xave

	cursor

	erase
	box
	ptype 3 20
	points x xave

	error_y x xave err

	relocate 0 0
	draw 130 0

	cursor
	ctype red
	connect x xave
	ctype 0
	error_y x xave err
	ctype 0