;*************************************************
; ce_3.ncl
;
; Concepts illustrated:
;   - Drawing color-filled contours over a cylindrical equidistant map
;   - Selecting a different color map
;   - Changing the contour level spacing
;   - Turning off contour lines
;   - Comparing styles of map tickmarks labels
;   - Changing the stride of the labelbar labels
;   - Zooming in on a particular area on the map
;   - Turning off the addition of a longitude cyclic point
;
;************************************************
;
; These files are loaded by default in NCL V6.2.0 and newer
 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
;************************************************
; open file and read in data
;************************************************
fname = "may.txt"

  n_col = numAsciiCol(fname)
  n_var = n_col
  n_pt  = numAsciiRow(fname)
;  mydata  = asciiread(fname,(/n_pt,n_var/),"float")

;other way of reading
 mydata=readAsciiTable("may.txt",5,"float",0)

 longitude = mydata(:,2)
 latitude = mydata(:,1)
 variable = mydata(:,3)

;************************************************
; create plot
;************************************************
;  wks = gsn_open_wks("png" ,"ce")      ; send graphics to PNG file
  wks = gsn_open_wks("x11","ce")

  res                       = True     ; plot mods desired

  res@gsnMaximize           = True     ; Make plot fit the frame
  res@cnFillOn              = True     ; turn on color fill
  res@cnLinesOn             = False    ; turn of contour lines
  res@cnLevelSpacingF       = 0.5      ; contour spacing
  res@cnFillPalette         = "BlAqGrYeOrRe"
  res@lbOrientation         = "Vertical"

  res@gsnAddCyclic          = False    ; data already has cyclic point
				       ; this must also be set for any zoom

;
; Note that the gsn_csm_*map* templates automatically set 
; res@mpLimitMode="LatLon" for you. If you are plotting a 
; different projection, you may have to set this resource.
;
  res@mpMinLatF            = -30      ; range to zoom in on
  res@mpMaxLatF            =  30.
  res@mpMinLonF            =  -70.
  res@mpMaxLonF            = 100.
  res@mpCenterLonF = 60.

  res@tiMainString = "Default map tickmark labels"
;  plot = gsn_csm_contour_map(wks,variable(0,0,{-30:30},{-70:100}), res)

  res@tiMainString          = "pmTickMarkDisplayMode = 'Always'"
  res@pmTickMarkDisplayMode = "Always"; use NCL default lat/lon labels
  res@pmTitleZone           = 4
;  plot = gsn_csm_contour_map(wks,variable(0,0,{-30:30},{-70:100}), res)
 contour = gsn_csm_contour_map(wks,variable,res)

end