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

begin

; Set up the arrays to plot.
  num_elems = 128
  xvals = ispan(1, num_elems, 1)
  yvals = new(dimsizes(xvals), double)

  ymin = 1.0D-15
  ymax = 1.0D-8

  i_start = 0
  i_end = num_elems-2
  yvals(i_start:i_end:2) = ymax
  i_start = 1
  i_end = num_elems-1
  yvals(i_start:i_end:2) = ymin

; Set up plot resources.
  res = True
  res@trXLog = True			; Use log scale for x axis.
  res@trYLog = True			; Use log scale for y axis.
  res@trXMinF = min(xvals)*1.0D-1	; Set the minimum x-axis value.
  res@trXMaxF = max(xvals)*1.0D+1	; Set the maximum x-axis value.
  res@trYMinF = min(yvals)*1.0D-1	; Set the minimum y-axis value.
  res@trYMaxF = max(yvals)*1.0D+1	; Set the maximum y-axis value.
  res@tiMainString \			; Set the plot title.
    = "ymin = " + ymin + ";  ymax = " + ymax

; Generate the plot.
  wks_type1 = "png"
  wks_type1@wkWidth = 1000					; Set width of png file.
  wks_type1@wkHeight = 1000					; Set height of png file.
  filename = "log_plot_ymax_" + ymax				; Set name of png file.
  wks_png = gsn_open_wks(wks_type1, "log_plot_ymin_" + ymin)	; Create workstation in which to generate a png file.
  plot_png = gsn_csm_xy(wks_png, xvals, yvals, res)		; Generate plot as a png file.

end