[gradsusr] Displaying data from NetCDF; outputting text files; using comparitive statistics
James Ciarlo`
james.ciarlo at physics.org
Thu Dec 16 07:38:53 EST 2010
Dear Muhammad,
The problem with the nc file is now solved thank you. I will contact the
RegCNET to understand better the process that produces the nc files so that
I can understand the problem with that file.
The processing that I was doing was from the ESRL web site, to obtain a
select region and time frame. But that I can do with GrADS so it is not a
problem.
Regarding the fprintf. I need to
sdfopen input.nc
set lon x
set lon y
set lev z #so one value for each, one point in the map
set t 1 150 #so basically I am setting a time line
d prmsl # this gives me a graph of pressure v time
#Then from fprintf I need to get the values for both pressure and time
I use 'frpintf prmsl data.txt' to get the pressure values
But then I need to get the corresponding time values, even in a separate
text document, it doesn't matter, as long as I can get it.
DO you think it's possible?
James
On 15 December 2010 16:16, Muhammad Rahiz <muhammad.rahiz at ouce.ox.ac.uk>wrote:
>
>
> --
> Muhammad Rahiz
> Researcher & DPhil Candidate (Climate Systems & Policy)
> School of Geography & the Environment
> University of Oxford
>
> On Wed, 15 Dec 2010, James Ciarlo` wrote:
>
> Dear Muhammad,
>>
>> A) I have sent you the nc file for file3.jpg, but I cannot send you the nc
>> file for file1.jpg
>> and file2.jpg as it is 35 GB large. Perhaps we can figure it out through
>> this one?
>>
>
> The attached ESRL_SLP.nc file has undergone some processing. You can look
> at the history of commands on the file by
>
> $ ncdump -h ESRL_SLP.nc
>
> I went the source of the data at
> www.esrl.noaa.gov/psd/data/gridded/data.20thC_ReanV2.monolevel.mm.html and
> downloaded the file prmsl.mon.mean.nc (it is the same file you have
> judging from the file history). I then made a test plot in GrADs (see
> prmsl.png). Plots fine.
>
> As I said, some processing was done on the file you have. I don't know
> exactly what language (I suspect NCL) and what it's trying to do. Perhaps
> you can tell what is it that you're trying to do with the file, I could
> possibly help.
>
>
>
>> B) I have set up the script fprintf.gs and have managed to get it
>> operational. It works well
>> and I thank you for it. I haven't been able to produce the text for time
>> and elevation though.
>> I tried the same procedure as you mentioned for lon.txt and lat.txt for
>> time, but it didn't
>> work? does it require another script or maybe a different way to define
>> time?
>>
>
> I'm not sure what you mean by wanting to get the ascii grid for time. Each
> ascii that you generate corresponds to a particular time. Hence if you want
> to get ascii grids for all time steps, just do something like
>
> 'sdfopen input.nc'
> 'set t 1'
> 'd prmsl'
> 'fprintf prmsl prmsl.t1.txt'
>
> 'set t 2'
> 'd prmsl'
> 'fprintf prmsl prmsl.t2.txt'
>
> Of course, you can do this in a loop for all time steps.
>
> I'm not sure if elevation (topography) is a variable of climate data (I've
> not come across any). Do you mean pressure levels like 500mb, 100mb etc? If
> yes, then you can do;
>
> 'set lev 500'
> 'set t 1'
> 'd prmsl'
> 'fprintf prmsl prmsl.time1.lev500.txt'
>
> This gives you the data for 500mb pressure level at time, t=1.
>
>
>
> Regards,
>>
>> James
>>
>> On 15 December 2010 10:46, Muhammad Rahiz <muhammad.rahiz at ouce.ox.ac.uk>
>> wrote:
>> Hi James,
>>
>> I suspect a corrupted data file. Could you attach the original
>> datafile, if it's
>> not too big? And attach the commands that you use to plot as well.
>>
>> --
>> Muhammad Rahiz
>> Researcher & DPhil Candidate (Climate Systems & Policy)
>> School of Geography & the Environment
>> University of Oxford
>>
>> On Wed, 15 Dec 2010, James Ciarlo` wrote:
>>
>> Dear Muhammad,
>> I am sorry it took me so long to answer. Thank you for your
>> answer on point 2.
>>
>> Regarding point 1, opening .nc files. I have attached some
>> files.
>> The images from file1.jpg and file2.jpg are grads images
>> (printim) from nc files produced with RegCM4, one is gxout
>> contour and the other is gxout shaded.
>> The image from file3.jpg is a grads image (printim) gxout shaded
>> for an nc file from the ESRL database.
>> The last image was produced with the PANOPLY data viewer from
>> the same file that produced file3.jpg
>>
>> As you can see the data is not being plotted with grads as with
>> normal .ctl files (which are working properly).
>> I cannot seem to understand why it is not reading it properly.
>> Maybe there are some definitions that I have to set? How should
>> I check if all the settings are correct?
>>
>> Regarding point 3, I think I can do them as a normal
>> mathematical expression, but I'll be trying that later on.
>>
>> Regards,
>>
>> James
>>
>> On 11 December 2010 12:24, James Ciarlo`
>> <james.ciarlo at physics.org> wrote:
>> Dear Muhammad,
>> I just had a look at it this morning. Unfortunately I
>> haven't yet had the time to put it to use. Thank you very
>> much for your help. I will get back to you about it for
>> sure. Thanks again
>>
>> Regards,
>>
>> James
>>
>>
>> On 11 December 2010 09:59, Muhammad Rahiz
>> <muhammad.rahiz at ouce.ox.ac.uk> wrote:
>> Hi James,
>> I was wondering if you got my reply to the
>> query you posted because I'm not sure if it
>> gets delivered successfully.
>>
>> Anyway, if you did not, these are what I
>> suggested
>>
>> 1. display error
>> - Try set gxout to something other than the
>> default e.g. set gxout grfill
>> - set clevs
>> - check units
>>
>> 2. print to ascii
>> what you need is the fprintf.gs script
>> available athttp://
>> cookbooks.opengrads.org/index.php?title=Recipe-002:_Savi
>>
>> ng_GrADS_variable_data_to_a_text_file
>>
>> Copy the code and name the file as fprintf.gs.
>> Then do the following,
>>
>> sdfopen input.nc
>> d var # where var = variable
>> fprintf var dat.txt # prints data of var
>> fprintf lon lon.txt # prints corresponding
>> lon
>> fprintf lat lat.txt # prints corresponding
>> lat
>>
>> 3. statistical analysis
>> I know how to do so in R. If you're interested
>> in using R for this purpose, I can help.
>>
>> HTH,
>>
>> --
>> Muhammad Rahiz
>> Researcher & DPhil Candidate (Climate Systems
>> & Policy)
>> School of Geography & the Environment
>> University of Oxford
>>
>> On Fri, 10 Dec 2010, James Ciarlo` wrote:
>>
>> Dear all,
>> I am using GrADS 2.0.a9 on LINUX. I am
>> trying to compare measured and modelled
>> data by using GrADS. However since I am
>> new with the program, there are
>> some issues that I cannot seem to figure
>> out, or find a solution to understand.
>> I am experiencing:
>>
>> 1) Difficulty with displaying data from
>> NetCDF files
>> I have opened the file with the command
>> 'sdfopen'
>> When I tried 'd prmsl' I got the
>> following error:
>> Operation error: Invalid dimension
>> environment
>> Min longitude > max longitude: 320 144
>> So I used ' set lon -40 145' and tried
>> the display command again
>> I got the following line and the image
>> attached (ncimage.jpg):
>> Contouring: 99000 to 102300 interval 300
>> And I am getting similar results with
>> other nc files
>>
>> 2) Difficulty with finding a command to
>> output text files, or dat, or anything
>> similar.
>> I have used set lat, set lon, and set
>> lev to obtain one value, and set t to
>> get a long time interval, I have used d
>> psa to display the time series, I
>> can use printim file.jpg to get an
>> image, but I cannot find a command to
>> produce a file.txt so that I can make
>> use of the actual numbers for
>> statistical purposes.
>>
>> 3) Difficulty with finding a command to
>> work out comparative statistics,
>> particularly correlation and
>> significance.
>>
>> Regards,
>>
>> James Ciarlo`
>>
>>
>>
>>
>>
>>
>>
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