[ncl-talk] How to set the time to get the composite map?

[Mary Haley]

Atul,

Your 14 MB file was too large for ncl-talk, but it still came to me because
I'm one of the administrators.

The averaging would still work close to the same way, but I'm not exactly
clear on what kind of average you want.

You have 40 years of data, so averaging for every 5 years is going to give
you 8 x 251 x 263:

  temp_5year_avg = dim_avg_n(reshape(temp,(/ntim5,5,nlat,nlon/)),1)   ; 8 x
251 x 263

I'm not exactly sure what you mean by a composite plot.  I think a "raster
fill" plot is similar to what you want, but again, I don't know how you
want to "composite" across the 8 sets of lat/lon data, so this is something
you will need to figure out.

I suggest looking through some of our examples at:

http://www.ncl.ucar.edu/Applications/

In particular, here are some samples of raster plots:

http://www.ncl.ucar.edu/Applications/raster.shtml

There are many other places where raster plots are used:

http://www.ncl.ucar.edu/Applications/classification.shtml
http://www.ncl.ucar.edu/Applications/gfed.shtml
http://www.ncl.ucar.edu/Applications/HiResPrc.shtml

For even more examples, go to our tips page:

http://www.ncl.ucar.edu/Applications/concepts_list.shtml

and use your browser search to look for "Drawing raster contours".

To help you get started, I've created a script that creates a "panel" plot
of each of your 8 averaged lat/lon grids. In order to get better outlines
of the map, since you have a small regional area, I used a shapefile of
India downloaded from:

https://gadm.org/download_country_v3.html

Please look at this code and try understand it before posting another
question. For documentation on dim_avg_n, or any of the NCL functions, go
to:

http://www.ncl.ucar.edu/Document/Functions/list_alpha.shtml

Here's the direct link to dim_avg_n and reshape:

http://www.ncl.ucar.edu/Document/Functions/Built-in/dim_avg_n.shtml
http://www.ncl.ucar.edu/Document/Functions/Built-in/reshape.shtml

If you do have a follow-up question, post it back to ncl-talk and not to me
individually.

Good luck,

--Mary




On Mon, Nov 12, 2018 at 9:32 AM, Atul Saini <atulsainimail at gmail.com> wrote:

> Thanks for guidance ma'am. Actually ma'am my query was related to the
> composite map and not xy plot. I am sorry to say ma'am that  mistakenly
> attached the wrong file (i.e. file containing fieldmean) with the earlier
> mail. Now, I am attaching the correct one (i.e. each grid point has some
> value) with this mail. Ma'am, the procedure to be followed to draw the
> filled in contour map/choropleth map (i.e. composite  map of 5 years). Will
> the process will remain same as suggested by you or does it require some
> changes?
> Regards,
>
>
>
>
> On Mon, Nov 12, 2018 at 9:08 PM Mary Haley <haley at ucar.edu> wrote:
>
>> Dear Atul Saini,
>>
>> If you are new to NCL, I suggest looking at the NCL User Guide which has
>> an excellent step-by-step guide for NCL, with a focus on creating graphics:
>>
>> http://www.ncl.ucar.edu/Document/Manuals/NCL_User_Guide/
>>
>> One way to do this is to first reshape the temperature array to an NTIM x
>> 5 x NLAT x NLON array, where NTIM is the total number of years divided by
>> five. Once you do this, you can use dim_avg_n to average across the
>> rightmost three dimensions of the new array, effectively giving you the
>> average for every 5 years:
>>
>>   filename = "chamba_tmean_fldmean.nc"
>>   a = addfile(filename,"r")
>>
>>   temp  = a->t
>>   dims  = dimsizes(temp)
>>   ntim  = dims(0)
>>   nlat  = dims(1)
>>   nlon  = dims(1)
>>   ntim5 = ntim/5
>> ;
>>
>> ; Reshape temperature array so we can easily average groupings of
>> ; five years at a time.
>>
>> ;
>>
>>   temp_5year_avg = dim_avg_n(reshape(temp,(/
>> ntim5,5,nlat,nlon/)),(/1,2,3/))
>>
>> The temp_5year_avg array will be a one-dimensional array of ntim5 (8)
>> elements that you can easily plot. See attached script and image.
>>
>> Note that your "t" variable on the file has no units, and it appears to
>> have a funny character as part of the long_name. You probably should try to
>> fix these when creating the plot.
>>
>> --Mary
>>
>>
>> On Sat, Nov 10, 2018 at 2:10 AM, Atul Saini <atulsainimail at gmail.com>
>> wrote:
>>
>>> Sir/Ma'am,
>>>                    I have the mean temperature file containing the data
>>> for MAMJJA season. This file contains the seasonal average (MAMJJA) data of
>>> each year from 1975 to 2014. I can easily plot the XY plot using it but the
>>> problem is how to make the average of 1975 to 1979, 1980 to 1985 and so on.
>>> I want to make the pentad map as explained in the previous sentence.
>>>
>>> Please help in making the average of five years to plot the map, which
>>> will represent the composite of five years.
>>>
>>> The data file is attached herewith this mail.
>>>
>>> Regards,
>>>
>>>
>>>
>>> _______________________________________________
>>> ncl-talk mailing list
>>> ncl-talk at ucar.edu
>>> List instructions, subscriber options, unsubscribe:
>>> http://mailman.ucar.edu/mailman/listinfo/ncl-talk
>>>
>>>
>>
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