Date: Wed Apr 17 2013 - 19:02:56 MDT
Hi Dave,
Many thanks for the solution. With these ideas and some further development I could get what I wanted. Attached is the final plot. The difference between two of the contours is shown at the 300hPa level, the desired result.
Regards,
Mark.
[cid:2831E436-D77A-4994-AD26-C1FAD556607E@dar.csiro.au]
On 17/04/2013, at 3:43 PM, David Brown <dbrown@ucar.edu<mailto:dbrown@ucar.edu>> wrote:
Hi Mark,
The immediate cause of the error message is that when you set gsnYAxisIrregular2Linear = True, the gsn code does an overlay behind
the scenes onto an "irregular" plot. This means that plot0 is no longer itself a contour plot. The contour plot id is available as an attribute of plot0.
So the get_isolines call needs be:
isolines = get_isolines(plot0@contour,(/2.0/))
However, it turns out that there are still some issues with this scenario and get_isolines needs some more work. When not over a map, get_isolines is
returning values in a low-level coordinate system rather than as data coordinates. However, there is a workaround that should give you what you want:
Set trGridType = "TriangularMesh". In this mode it does return data coordinates and also it linearizes the YAxis without using the special gsnYAxisIrregularToLinear resource.
I am attaching a revised version of your plot that works. I also modified the polyline drawing code to draw a line on top of the
original contour line using the returned coordinate values to demonstrate that they do match. Note that if you only ask for one level get_isolines returns an array not a list.
Hope this helps.
-dave
<plot_davetest-new.ncl>
On Apr 16, 2013, at 6:09 PM, <Mark.Collier@csiro.au<mailto:Mark.Collier@csiro.au>> wrote:
Hi Dave,
I put the script plot_davetest.ncl and input data file davetest.nc in the incoming area. I tried it under both 6.1.1 and 6.1.2 with same error.
uname -a
Linux dcc 2.6.18-348.3.1.el5 #1 SMP Mon Mar 11 19:39:25 EDT 2013 x86_64 x86_64 x86_64 GNU/Linux
Regards,
Mark.
On 17/04/2013, at 5:57 AM, David Brown <dbrown@ucar.edu<mailto:dbrown@ucar.edu>> wrote:
Hi Mark,
I'm sorry to hear you are having problems with this routine. I just ran a test using the plot value returned from
gsn_csm_contour as the input to get_isolines pretty much as you have it here. It ran without problems. I tried it both
with my development version of NCL on my mac and on our cluster using the release version of 6.1.2.
I would be happy to take a look at your code (and sufficient data to get it to run) to see if there is some other factor
coming into play here. I think you know the upload routine but just in case for reference it is detailed at http://www.ncl.ucar.edu/report_bug.shtml.
-dave
On Apr 15, 2013, at 10:44 PM, <Mark.Collier@csiro.au<mailto:Mark.Collier@csiro.au>> wrote:
Hi Dave,
the interface looked simple enough but my best attempt gave:
fatal:NhlGetIsoLines: invalid contourplot id
fatal:NhlGetIsolines: error retrieving isolines
fatal:["Execute.c":8128]:Execute: Error occurred at or near line 251 in file plot_tropoh_climdiff.ncl
what I tried was:
plot0=gsn_csm_contour(wks,clim1_hist_ea,conres2)
isolines = get_isolines(plot0,(/2.0/))
where plot0 renders normally, and it contains the 2.0 contour level.
I'm using version 6.1.2
Thanks,
Mark.
________________________________________
From: David Brown [dbrown@ucar.edu<mailto:dbrown@ucar.edu>]
Sent: Tuesday, 16 April 2013 4:01 AM
To: Collier, Mark (CMAR, Aspendale)
Cc: ncl-talk@ucar.edu<mailto:ncl-talk@ucar.edu>
Subject: Re: obtain values of a single contour
Hi Mark,
I recently created a function that will do what you want. It is available in NCL 6.1.1 and later. Check out:
http://www.ncl.ucar.edu/Document/Functions/Built-in/get_isolines.shtml
-dave
On Apr 15, 2013, at 12:41 AM, <Mark.Collier@csiro.au> wrote:
Hi,
I plot a single unique contour of a 2d array using @cnLevels = val using the gsn_csm_contour function.
is there a way of obtaining the x-y values of that line from the plot?
Regards,
Mark.
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