load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/gsn_code.ncl"
load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/gsn_csm.ncl"

begin 
  npts = 500
  x    = fspan(-100,100,npts)                 ; 500 values from -100 to 100.
  y    = asciiread("xy2.txt",(/npts,4/),"float")

  wks = gsn_open_wks ("x11","xy2_ex01")

  res  = False                        ; No plot options desired.
  plot = gsn_csm_xy(wks,x,y(:,0),res) ; Call the gsn_csm function
                                      ; for drawing one curve.
end