Re: missing data

I would suggest looking at:

Example 8: http://www.ncl.ucar.edu/Applications/conOncon.shtml
Maybe even Example 4

==

http://www.ncl.ucar.edu/Support/talk_archives/2009/0392.html

On 10/9/11 12:50 PM, Mary Haley wrote:
> Xiaoyan,
>
> You cannot overlay one map plot on another using "overlay". The base
> plot needs to be a map plot, and the overlaid plot should simply be a
> contour or a vector plot, for example.
>
> So, change your "plot2" line to call "gsn_csm_contour":
>
> plot2 = gsn_csm_contour(wks,var2,res2) ; draw second plot
>
> You can see some overlay examples at:
>
> http://www.ncl.ucar.edu/Applications/overlay.shtml
>
>
> --Mary
>
> On Oct 8, 2011, at 8:24 AM, Xiaoyan Ma wrote:
>
>> Hi Adam,
>>
>> Continue with my last question.
>>
>> Now I want to make a plot with one overlay on another. The data for
>> the first plot have all values available, and second data have many
>> missing values (as my earlier question). I used overplay command to
>> try to put second on the first. Please see ncl script below. It didn't
>> work since I got 2 plots instead one overlay plot. the error info is
>>
>> fatal:NhlAddOverlay: plot class mapPlotClass cannot be overlay plot member
>>
>> it looks like mapplot could be be overlay?
>>
>> could you help me to fix the problem? thanks!
>>
>> Xiaoyan
>>
>> =========================================================
>> begin
>>
>> nlat = 46
>> nlon = 72
>>
>> setfileoption("bin","ReadByteOrder","BigEndian")
>> var = fbindirread("0.dat",0, (/46,72/), "float")
>> ;=============================
>> ; create lat and long coordinate variables
>> ;============================
>> dlat = 180./nlat
>> dlon = 360./nlon
>>
>> var!0 = "lat"
>> var&lat = ispan(-23,22,1)*dlat
>> var&lat@units = "degrees_north"
>>
>> var!1 = "lon"
>> var&lon = ispan(-36,35,1)*dlon
>> var&lon@units = "degrees_east"
>> ;**************************************************
>> ; create plot
>> ;**************************************************
>> wks = gsn_open_wks("ps","overlay")
>>
>> gsn_define_colormap(wks,"BlAqGrYeOrReVi200") ; choose colormap
>>
>> res = True ; plot mods desired
>> res@cnFillOn = True ; turn on color
>> res@cnLinesOn = False ; no contour lines
>>
>> res = True ; plot mods desired
>>
>> res@tiMainString = "Explict Contour Levels"
>> res@cnFillOn = True ; turn on color fill
>> res@cnLinesOn = False ; turn of contour lines
>> res@gsnSpreadColors = True ; use full range of color map
>> res@gsnSpreadColorStart = 20 ; color to start
>> res@gsnSpreadColorEnd = 193 ; color to end
>>
>> res@lbOrientation = "vertical" ; vertical label bar
>>
>> res@pmTickMarkDisplayMode = "Always"; use NCL default lat/lon labels
>> res@gsnAddCyclic = False ; data already has cyclic point
>> ; this must also be set for any zoom
>>
>> res@cnLevelSelectionMode = "ExplicitLevels" ; set explicit contour levels
>> res@cnLevels = (/1e-4,5e-4,1e-3,5e-3,0.01,0.02,0.03,0.04,0.05/)
>> ;===========================
>> ; plot parameters
>> ;===========================
>> res@gsnDraw = False ; do not draw
>> res@gsnFrame = False ; do not advance frame
>>
>> plot1 = gsn_csm_contour_map_ce(wks,var,res) ; draw 1st contour
>> ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
>>
>> var2 = fbindirread("1.dat",0, (/46,72/), "float")
>>
>> var2!0 = "lat"
>> var2&lat = ispan(-23,22,1)*dlat
>> var2&lat@units = "degrees_north"
>>
>> var2!1 = "lon"
>> var2&lon = ispan(-36,35,1)*dlon
>> var2&lon@units = "degrees_east"
>>
>> var2@_FillValue = 0.0001 ; sets _FillValue to 0.0001
>>
>> res2 = True ; plot mods desired
>> res2@cnFillOn = True ; turn on color
>> res2@cnLinesOn = False ; no contour lines
>>
>> res2@tiMainString = "Explict Contour Levels"
>> res2@cnFillOn = True ; turn on color fill
>> res2@cnLinesOn = False ; turn of contour lines
>> res2@gsnSpreadColors = True ; use full range of color map
>> res2@gsnSpreadColorStart = 20 ; color to start
>> res2@gsnSpreadColorEnd = 193 ; color to end
>>
>> res2@lbOrientation = "vertical" ; vertical label bar
>>
>> res2@pmTickMarkDisplayMode = "Always"; use NCL default lat/lon labels
>> res2@gsnAddCyclic = False ; data already has cyclic point
>> ; this must also be set for any zoom
>> res2@cnLevelSelectionMode = "ExplicitLevels" ; set explicit contour levels
>> res2@cnLevels = (/1e-4,5e-4,1e-3,5e-3,0.01,0.02,0.03,0.04,0.05/)
>>
>> res2@cnFillMode = "RasterFill"
>>
>> plot2 = gsn_csm_contour_map_ce(wks,var2,res2) ; draw second plot
>>
>> overlay(plot1,plot2) ; now over lay plots
>>
>> ; the result of the overlay procedure is that the second argument is
>> ; placed on top of the first. The first plot (now combined) is returned.
>>
>> ; these two step are required!
>> draw(plot1) ; note we are drawing the first one!
>> frame(wks)
>>
>> end
>>
>> On 10/05/11, *"Xiaoyan Ma" * <xiaoyan.ma@asrc.albany.edu
>> <mailto:xiaoyan.ma@asrc.albany.edu>> wrote:
>>> Hi Adam,
>>>
>>> Thanks for the quick reply. I did all except the last one. Now it works.
>>>
>>> Thanks very much for the help.
>>>
>>> Xiaoyan
>>>
>>> On 10/05/11, *Adam Phillips * <asphilli@ucar.edu
>>> <mailto:asphilli@ucar.edu>> wrote:
>>>> Hi Xiaoyan,
>>>> There might be a few problems here. Are you getting any error messages?
>>>> I would guess that you are... If you are the next time you send a
>>>> question to ncl-talk please include any error messages that you are
>>>> getting...
>>>>
>>>> Does your var array have latitude/longitude coordinate variables
>>>> assigned to it? From the snippet of code you sent I don't see them..
>>>> You are reading in your data from a binary file, but when you do that
>>>> there will not be any information associated associated with your data
>>>> array that describes it. So, you need to assign that information to
>>>> your
>>>> var array:
>>>>
>>>> var!0 = "lat"
>>>> var&lat = ispan(-90,90,4) ; I am guessing that your latitudes run from
>>>> ; -90:90 by 4.. You may need to change this.
>>>> var&lat@units = "degrees_north"
>>>>
>>>> var!1 = "lon"
>>>> var&lon = ispan(0,355,5) ; I am guessing that your longitudes run from
>>>> ; 0:355 by 6.. You may need to change this.
>>>> var&lon@units = "degrees_east"
>>>>
>>>> By default, NCL will color fill areas denoted by the _FillValue
>>>> attribute as white. So you need to make sure that var@_FillValue is set
>>>> appropriately:
>>>>
>>>> var@_FillValue = ; set _FillValue, where data is missing, to the
>>>> ; appropriate value
>>>>
>>>> Finally, and this might be most important, if your var array is mostly
>>>> composed of missing data, you are going to want to tell NCL to Raster
>>>> Fill, instead of Area Fill.. Going to Raster Fill will show each
>>>> individual grid box, while Area Fill may or may not.. So, add this:
>>>>
>>>> res@cnFillMode = "RasterFill"
>>>>
>>>> to your resource list.
>>>>
>>>> If that advice doesn't solve your issue, please respond back to
>>>> ncl-talk.. Adam
>>>>
>>>>
>>>> On 10/05/2011 10:27 AM, Xiaoyan Ma wrote:
>>>> > Hi
>>>> >
>>>> > I want to create a contour plot from the observational data, i.e.
>>>> for a
>>>> > 46*72 grid there are only ~ 100 points with observations, other points
>>>> > with missing data (I set a value as 0.0001). when I use ncl as
>>>> below, I
>>>> > want to let those points with missing data as WHITE, but others as
>>>> > color. I do so in 2 ways:
>>>> >
>>>> > 1) set missing data as mask
>>>> > 2) set missing data as FillValue
>>>> >
>>>> > I do see there are values of non-0.0001 by using print, but the
>>>> > contour looks all white from 1) or 2). anybody tell me what is wrong?
>>>> >
>>>> > thanks a lot.
>>>> >
>>>> > Xiaoyan
>>>> >
>>>> >
>>>> --------------------------------------------------------------------------
>>>> > var = fbindirread("1.dat",0, (/46,72/), "float")
>>>> >
>>>> > print(var)
>>>> > ; var = mask(var,var.le.0.001,False) ; create
>>>> > artificial areas of missing data
>>>> >
>>>> > var@_FillValue = 0.0001 ; sets _FillValue to
>>>> > 0.0001
>>>> >
>>>> > res = True ; plot mods desired
>>>> > res@cnFillOn = True ; turn on color
>>>> > res@cnLinesOn = False ; no contour lines
>>>> >
>>>> > plot= gsn_csm_contour_map_ce(wks,var,res)
>>>> >
>>>> >
>>>> > _______________________________________________
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>>>>
>>>> --
>>>> ______________________________________________________________
>>>> Adam Phillips asphilli@ucar.edu <mailto:asphilli@ucar.edu>
>>>> NCAR/Climate and Global Dynamics Division (303) 497-1726
>>>> P.O. Box 3000
>>>> Boulder, CO 80307-3000 http://www.cgd.ucar.edu/cas/asphilli
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Received on Sun Oct 9 19:56:12 2011