# Re: Question about contour plots

From: Mary Haley <haley_at_nyahnyahspammersnyahnyah>
Date: Fri Aug 12 2011 - 10:57:06 MDT

Hi all,

This was resolved offline. Yaosheng found this example page, which worked:

--Mary

On Aug 8, 2011, at 11:57 AM, Yaosheng Chen wrote:

> Hi Mary,
>
> Thank you for the script. I understand what you are talking now.
>
> What I'm talking about is, what if the levels are also a two dimension
> data set (levels vs time).
>
> Use your script as an example. Assuming for the first half of data
> (that is, data(:,0:(ntim / 2 - 1))), the levels are (/1000, 925, 850,
> 750, 600, 500, 400, 250, 100./). However, the second of data
> (data(:,(ntim / 2 : (ntim - 1)))) are located at levels (/1000, 900,
> 850, 750, 600, 500, 400, 250, 100./).
>
> Is there any way to make plots for that?
>
> Thanks,
> Yaosheng
>
> On Fri, Aug 5, 2011 at 3:41 PM, Mary Haley <haley@ucar.edu> wrote:
>> Yaosheng,
>>
>> It depends on how dramatically your pressure values change.
>>
>> We have a pressure/height versus time example page:
>>
>> http://www.ncl.ucar.edu/Applications/height_time.shtml
>>
>> These pressure values look something like 1000, 925, 850, 750, 600, 500, 400, 250, 100.
>>
>> If you try to plot something where your values are regularly spaced for a bit, and then suddenly change drastically, then you will get a warning and possibly the wrong plot:
>>
>> warning:_NhlCreateSplineCoordApprox: Attempt to create spline approximation for Y axis failed: consider adjusting trYTensionF value
>>
>> Run this script to see what I'm talking about. The data for the second frame has a very irregular "lev" coordinate array which causes a spline warning and the Y axis is then just index values.
>>
>>
>>
>> begin
>> ;---Generate some dummy data.
>> level = (/1000, 850, 700, 500, 400, 300, 250, 200, 150, 100/)
>> time = ispan(1,40,2)
>>
>> ntim = dimsizes(time)
>> nlev = dimsizes(level)
>> data = generate_2d_array(10, 12, -20., 17., 0, (/ nlev,ntim/))
>>
>> ;---Name the dimensions and attach coordinate arrays
>> data!0 = "lev"
>> data!1 = "time"
>> data&lev = level
>> data&time = time
>>
>> ;---Start the graphics
>> wks = gsn_open_wks("x11","ph")
>> gsn_define_colormap(wks,"rainbow")
>>
>> ;---Set some plot options
>> res = True
>> res@gsnMaximize = True ; Maximize plot in frame
>> res@gsnSpreadColors = True ; Span full color map
>> res@cnFillOn = True ; Turn on contour fill
>> res@cnLinesOn = False ; Turn off contour lines
>> res@lbLabelAutoStride = True ; Control labelbar spacing
>>
>> ;---This plot is fine, no warnings.
>> plot = gsn_csm_contour(wks,data,res)
>>
>> ;---Change the levels. You will get a spline warning.
>> data&lev = (/1000, 950, 900, 850, 800, 750, 250, 200, 150, 100/)
>> plot = gsn_csm_contour(wks,data,res)
>>
>> ;---This removes the spline warning.
>> res@trYTensionF = 5.5
>> plot = gsn_csm_contour(wks,data,res)
>>
>>
>> end
>>
>>
>> On Aug 5, 2011, at 12:09 PM, Yaosheng Chen wrote:
>>
>>> Hi Mary,
>>>
>>>
>>> In fact it is just the pressure (P and PB) and wind speed derived from
>>> U and V in a WRF output file.
>>>
>>> I want to make a pressure vs time plot, with contours showing wind speed.
>>>
>>> The pressure for a given layer, for example the second layer from
>>> surface, changes slightly every time step. But when I make plots I
>>> just assume the pressure dimension does not change at all.
>>>
>>> Just curious if pressure change dramatically every time step, whether
>>> I can make a plot considering that change.
>>>
>>> Thanks.
>>> Yaosheng
>>>
>>> On Wed, Aug 3, 2011 at 5:24 PM, Mary Haley <haley@ucar.edu> wrote:
>>>> Yaosheng,
>>>>
>>>> I'm not sure I have enough information to answer your question.
>>>> Can you send me the output of doing "printVarSummary" on the
>>>> data array you want to plot?
>>>>
>>>> --Mary
>>>>
>>>>
>>>> On Aug 3, 2011, at 2:00 PM, Yaosheng Chen wrote:
>>>>
>>>>> Hi,
>>>>>
>>>>> Just out of curious, is it possible to make pressure vs hight contour
>>>>> plots with a data set that the number and values of pressure levels of
>>>>> which vary with time step without pre-processing the data (for example
>>>>> interpolate the data to some common pressure level)?
>>>>>
>>>>> Thanks,
>>>>> Yaosheng
>>>>> _______________________________________________
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>>>>
>>>>
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>>

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Received on Fri Aug 12 10:57:14 2011

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