; https://www.ncl.ucar.edu/Support/talk_archives/2013/3871.html (x lable)
; https://www.ncl.ucar.edu/Applications/Scripts/xy_7.ncl
; https://www.ncl.ucar.edu/Applications/xy.shtml (xy_25.ncl)
;****************************************************
; xy_7.ncl
;
; Concepts illustrated:
;   - Drawing an XY plot with two different Y axes
;   - Changing the title on the Y axis
;   - Changing the line dash pattern in an XY plot
;   - Changing the line color for multiple curves in an XY plot
;   - Setting the mininum/maximum value of the Y axis in an XY plot
;
;****************************************************
;
; 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"   
;****************************************************
begin
;***************************
; read in data
;***************************
 	data_col = asciiread("data.txt",31,"string")
	delim   = " "
	date	= str_get_field(data_col(1:),1,delim)
	prec	= tofloat(str_get_field(data_col(1:),2,delim))
	sm		= tofloat(str_get_field(data_col(1:),3,delim))
;	sm@_FillValue	= 9999

;***************************
; plot parameters
;***************************
	wks   = gsn_open_wks ("png","GPM_SMAP_20170401_30")                  ; send graphics to PNG file

; resources for "left" variable
  resL                  = True
  
  resL@gsnMaximize      = True
  resL@vpWidthF         = 0.8            ; Change the aspect ratio, but 
  resL@vpHeightF        = 0.4            ; make plot as large as possible.
  
  resL@trYMaxF           = max(prec)+1                  ; axis max
  resL@trYMinF           = min(prec)                    ; axis min
  resL@xyLineThicknessF = 2.                  ; thicker line
  resL@xyLineColor      = "blue"                   ; line color
  
  resL@tiYAxisFontColor = resL@xyLineColor
  
  resL@tiYAxisString = "Precipitation (mm/day)"  ; axis string
  resL@tiMainString      = "Precipitation and Soil Moisture"          ; title

; resources for "right" variable
  resR					= True                      
  resR@trYMaxF			= max(sm)                    ; axis max
  resR@trYMinF			= min(sm)                    ; axis min
  resR@xyDashPatterns	= 2                   ; dashed line for 2nd
  resR@xyLineThicknessF = 2                   ; thicker line
  resR@xyLineColor      = "red"                    ; line color
  
  resR@tiYAxisFontColor = resR@xyLineColor
  
;  resR@tmYRFormat       = "f"            ; Remove trailing zeros from labels
  
  resR@tiYAxisString = "Soil Moisture (cm~S~3~N~/cm~S~3~N~)"   ; axis string

	resL@tmXBMode	= "Explicit" ; explicit labels
	resL@tmXBValues = ispan(0,dimsizes(date)-1,1)
	resL@tmXBLabels = date
	
	plot = gsn_csm_xy2(wks,ispan(0,dimsizes(date)-1,1),prec,sm,resL,resR)

end