[ncl-talk] grid_area_avg
Guido Cioni
guidocioni at gmail.com
Tue Oct 17 03:35:31 MDT 2017
Why did you comment this line ?
> ;printVarSummary(aot_subset)
That would have helped you in debugging the error on your own.
You are using the re-assignment operator ":=". This means that every time you make an assignment the variable is created again. Thus, you cannot make this assignment
> aot_subset(ilt1:ilt2,iln1:iln2) := data(ilt1:ilt2, iln1:iln2)
as NCL has no way to know the shape of aot_subset beforehand.
The following should be used instead (notice the assignment with "=" in the second line).
aot_subset := data
aot_subset = aot_subset at _FillValue
aot_subset(ilt1:ilt2,iln1:iln2) = data(ilt1:ilt2, iln1:iln2)
Notice that this will (1) create an array which is shaped like data (2) fill it with fill values as you only want to compute the average over the subset (3) populate the array only in the lat-lon box provided. However I don't see why you would want to use such a complicated syntax when the following code would produce the same result
aot_subset_avg=avg(data(ilt1:ilt2, iln1:iln2))
If you have the right coordinate attributes you can even jump the first 7 lines and do
aot_subset_avg=avg(data({18:24},{74:78})
but I don't know your data.
As it was already suggested by Mary and others, PLEASE take time to debug the errors on your own.
Regards,
> On 17. Oct 2017, at 11:25, Kunal Bali <kunal.bali9 at gmail.com> wrote:
>
>
> I did the following changes but still getting an error of aot_subset which is undefined.
> please let me know that how to fix or defined the aot_subset this problem.
>
>
>
> latv = (/ 18, 24/) ; for extracting grid box data
> lonv = (/ 74, 78 /)
> nm = getind_latlon2d (lat2d, lon2d, latv, lonv)
> ilt1 = nm(0,0) ; start lat index
> ilt2 = nm(1,0) ; start lon index
> iln1 = nm(0,1) ; end lat index
> iln2 = nm(1,1) ; end lon index
> lat_subset := lat2d(ilt1:ilt2,iln1:iln2)
> lon_subset := lon2d(ilt1:ilt2,iln1:iln2)
> aot_subset := data
> aot_subset(ilt1:ilt2,iln1:iln2) := data(ilt1:ilt2, iln1:iln2)
>
> ;printVarSummary(aot_subset)
> aot_avg = avg(data)
> aot_subset_avg = avg(aot_subset)
>
> ;print(nm)
> print("-----")
>
> do k=0,dimsizes(latv)-1
> n = nm(k,0)
> m = nm(k,1)
> print(lat2d(n,m)+" "+lon2d(n,m))
> print(" "+data(:,n,m)) ; nearest grid point at all time steps
> print("-----")
> end do
>
>
>
>
> regards
> Kunal Bali
>
>
>
>
>
>
> On Tue, Oct 17, 2017 at 12:41 PM, Kunal Bali <kunal.bali9 at gmail.com <mailto:kunal.bali9 at gmail.com>> wrote:
> I have sent the ncl script and data to the incoming dir with the given names as
>
> data = maiactaotE.h00v03.20003660525-20003660700.nc.bz2
> ncl_script = extract_iiserb.ncl
>
> I am not able to define the var_subset in the given script.
> please let me know if you have received the data and script?
>
>
>
>
>
> Kunal Bali
>
>
>
>
>
>
> On Mon, Oct 16, 2017 at 11:07 PM, Mary Haley <haley at ucar.edu <mailto:haley at ucar.edu>> wrote:
> Kunal,
>
> You must make an effort to debug some of these problems on your own. The error is telling you that something is wrong around line 34 and it is telling you exactly what the problem is. Please try to fix this error.
>
> If you continue to have problems after fixing this error, then I need to ask you to provide the full script and data via ftp:
>
> http://www.ncl.ucar.edu/ftp_files.shtml <http://www.ncl.ucar.edu/ftp_files.shtml>
>
> However, make sure you debug any other new problems that come up, instead of just emailing them to ncl-talk. We have a page to help you understand some of NCL's errors, and what causes them:
>
> http://www.ncl.ucar.edu/Document/Language/error_messages.shtml <http://www.ncl.ucar.edu/Document/Language/error_messages.shtml>
>
> The particular error you're seeing can be found here:
>
> http://www.ncl.ucar.edu/Document/Language/error_messages.shtml#NumSubRHS <http://www.ncl.ucar.edu/Document/Language/error_messages.shtml#NumSubRHS>
>
> As a side note, you are running a 3-year old version of NCL. I suggest that you upgrade to NCL V6.4.0.
>
> --Mary
>
>
>
> On Mon, Oct 16, 2017 at 12:52 AM, Kunal Bali <kunal.bali9 at gmail.com <mailto:kunal.bali9 at gmail.com>> wrote:
> I simply include the code (which you mentioned) were I was taking the avg of the data as given below (please correct me if I did wrong)
>
>
> ;----------------------------------------------------------------------
> ; Main code
> ;----------------------------------------------------------------------
> dir = "./"
> fnames = systemfunc("ls " + dir + "maiactaot*.nc")
> print(fnames)
> a = addfile(fnames,"r")
> data = short2flt(a->Optical_Depth_055_grid1km)
> printVarSummary (data)
> printMinMax (data, 0)
> print("-----")
> nFill = num(ismissing(data))
> print("nFill="+nFill)
> print("-----")
>
> lat2d = a->GridLat_grid1km
> lon2d = a->GridLon_grid1km
> printMinMax (lat2d, 0)
> printMinMax (lon2d, 0)
> print("-----")
>
> ;---grid points of interest
> ;---http://www.ncl.ucar.edu/Document/Functions/Contributed/getind_latlon2d.shtml <http://www.ncl.ucar.edu/Document/Functions/Contributed/getind_latlon2d.shtml>
> ; latv = (/22, 24.0, 24.0, 22.0, 22.0/)
> ; lonv = (/76, 76.0, 78.0, 78.0, 76.0/)
>
> latv = (/ 22, 24/)
> lonv = (/ 76, 78 /)
> nm = getind_latlon2d (lat2d, lon2d, latv, lonv)
> ilt1 = nm(0,0) ; start lat index
> ilt2 = nm(1,0) ; start lon index
> iln1 = nm(0,1) ; end lat index
> iln2 = nm(1,1) ; end lon index
> var_subset = var(ilt1:ilt2,iln1:iln2)
> var_subset_avg = avg(var_subset)
>
> print(nm)
> print("-----")
>
> do k=0,dimsizes(latv)-1
> n = nm(k,0)
> m = nm(k,1)
> print(lat2d(n,m)+" "+lon2d(n,m))
> print(" "+data(:,n,m)) ; nearest grid point at all time steps
> print("-----")
> end do
>
>
>
>
>
> But still not getting the desired output as a single square box mean value . It is showing the errors as
>
> kunal at kunal-Vostro-1015:/media/Local Disk_/IIT_DELHI/2001/MAIACTAOT_TIME$ ncl extract1.ncl
> Copyright (C) 1995-2014 - All Rights Reserved
> University Corporation for Atmospheric Research
> NCAR Command Language Version 6.2.1
> The use of this software is governed by a License Agreement.
> See http://www.ncl.ucar.edu/ <http://www.ncl.ucar.edu/> for more details.
>
>
> Variable: fnames
> Type: string
> Total Size: 4 bytes
> 1 values
> Number of Dimensions: 1
> Dimensions and sizes: [1]
> Coordinates:
> (0) ./maiactaot.h00v02.20010040635-20011550640.nc <http://maiactaot.h00v02.20010040635-20011550640.nc/>
>
> Variable: data
> Type: float
> Total Size: 40320000 bytes
> 10080000 values
> Number of Dimensions: 3
> Dimensions and sizes: [time | 7] x [YDim_grid1km | 1200] x [XDim_grid1km | 1200]
> Coordinates:
> time: [8862.583333333314..12486.66666666669]
> Number Of Attributes: 8
> coordinates : GridLat_grid1km, GridLon_grid1km
> hdfeos_name : Optical_Depth_055
> projection : Albers Conical Equal_Area
> unit : None
> long_name : AOT at 0.55 micron
> _FillValue_original : -28672
> _FillValue : -28672
> valid_range : ( -0.1, 5 )
> (0) AOT at 0.55 micron: min=0 max=3.924
> (0) -----
> (0) nFill=6285271
> (0) -----
> (0) latitude: min=21.86737357453027 max=34.99855492029426
> (0) longitude: min=64.23634233372005 max=79.4747290253718
> (0) -----
> fatal:["Execute.c":7863]:Number of subscripts on right-hand-side do not match
> number of dimensions of variable: (2), Subscripts used: (3)
>
> fatal:["Execute.c":8578]:Execute: Error occurred at or near line 34 in file extract1.ncl
>
> fatal:Variable (var_subset) is undefined
> fatal:["Execute.c":8578]:Execute: Error occurred at or near line 35 in file extract1.ncl
>
>
>
>
> Variable: nm
> Type: integer
> Total Size: 16 bytes
> 4 values
> Number of Dimensions: 2
> Dimensions and sizes: [2] x [2]
> Coordinates:
> Number Of Attributes: 1
> long_name : indices closest to specified LAT/LON coordinate pairs
> (0,0) 1199
> (0,1) 792
> (1,0) 1199
> (1,1) 1041
> (0) -----
> (0) 23.76603307545667 75.53995171540016
> (0) 0.179
> (1) 0.142
> (2) -28672
> (3) 0.169
> (4) -28672
> (5) -28672
> (6) -28672
> (0) -----
> (0) 24.26559325846936 77.93996773594735
> (0) -28672
> (1) 0.393
> (2) -28672
> (3) 0.156
> (4) 0.313
> (5) -28672
> (6) -28672
> (0) -----
>
>
>
>
>
>
>
>
>
> Kunal Bali
>
>
>
>
>
> On Sat, Oct 14, 2017 at 12:24 AM, Mary Haley <haley at ucar.edu <mailto:haley at ucar.edu>> wrote:
> Kunal,
>
> Please include the code where you are actually taking the average of your data using the information returned from getind_latlon2d.
>
> It's important to note that getind_latlon2d simply returns the individual index values that are closest to each of the lat/lon pairs that you gave it. It doesn't work in such a way that you give it a lat/lon box and it returns all the values in that box.
>
> That's what I was trying to illustrate with the wrf_gsn_10.ncl I created. I gave the function two corners of the box, and then using the two pairs of index values I got back, I was able to get all the values inside the box area of interest:
>
> lats = (/ min_lat, max_lat /)
> lons = (/ min_lon, max_lon /)
> nm = getind_latlon2d (lat2d, lon2d, lats, lons)
> ilt1 = nm(0,0) ; start lat index
> ilt2 = nm(1,0) ; start lon index
> iln1 = nm(0,1) ; end lat index
> iln2 = nm(1,1) ; end lon index
> var_subset = var(ilt1:ilt2,iln1:iln2)
> var_subset_avg = avg(var_subset)
>
> --Mary
>
>
> On Thu, Oct 12, 2017 at 1:19 PM, Kunal Bali <kunal.bali9 at gmail.com <mailto:kunal.bali9 at gmail.com>> wrote:
> Dear Haley Ma'am,
>
> Thanks for providing the information and example.
> But if I follow the getind_latlon2d function as I did, then it seems like I followed the same procedure as given in the example http://www.ncl.ucar.edu/Document/Functions/Contributed/getind_latlon2d.shtml <http://www.ncl.ucar.edu/Document/Functions/Contributed/getind_latlon2d.shtml>
>
> But still I am not getting the mean of the grid box on every time step or am I reading incorrectly the result ?
>
>
> regards
> Kunal Bali
>
>
>
>
>
>
> On Fri, Oct 13, 2017 at 12:11 AM, Mary Haley <haley at ucar.edu <mailto:haley at ucar.edu>> wrote:
> Kunal,
>
> I created an example for you, showing three ways you can subset a WRF grid (since I already had a similar example). It shows how to use the getind_latlon2d function.
>
> You have to be careful with subsetting curvilinear data, because specifying a lat/lon box to take an average over can mean two different things. You will be able to see the difference when you look at the graphic.
>
> See example wrf_gsn_10.ncl at:
>
> http://www.ncl.ucar.edu/Applications/wrfgsn.shtml#ex10 <http://www.ncl.ucar.edu/Applications/wrfgsn.shtml#ex10>
>
> --Mary
>
>
>
> On Wed, Oct 11, 2017 at 12:03 PM, Kunal Bali <kunal.bali9 at gmail.com <mailto:kunal.bali9 at gmail.com>> wrote:
> Dear NCL users,
>
> Single point coordinates values of 23.0 N and 77.0 E is extracted or print by using the script below
>
> ----------------------------------------------------------------------
> ; Main code
> ;----------------------------------------------------------------------
> dir = "./"
> fnames = systemfunc("ls " + dir + "maiactaot*.nc")
> print(fnames)
> a = addfile(fnames,"r")
> data = short2flt(a->Optical_Depth_055_grid1km)
> nFill = num(ismissing(data))
> lat2d = a->GridLat_grid1km
> lon2d = a->GridLon_grid1km
>
> ;---grid points of interest
> latv = (/23.0/)
> lonv = (/77.0 /)
>
> nm = getind_latlon2d (lat2d,lon2d, latv, lonv)
>
> do k=0,dimsizes(latv)-1
> n = nm(k,0)
> m = nm(k,1)
> print(lat2d(n,m)+" "+lon2d(n,m)) ; grid point location
> print(" "+data(:,n,m)) ; nearest grid point at all time steps
> print("-----")
> end do
>
>
> NOW, I want to extract the square grid box of 100 km around the coordinates (23N,77E) such as
> latv = (/22, 24.0, 24.0, 22.0, 22.0/)
> lonv = (/76, 76.0, 78.0, 78.0, 76.0 /)
>
>
> after that I want to do the area mean of the grid box. So that I can get one single point value of that grid box.
> So when I replacing
> latv = (/23.0/)
> lonv = (/77.0/)
>
> with
>
> latv = (/22, 24.0, 24.0, 22.0, 22.0/)
> lonv = (/76, 76.0, 78.0, 78.0, 76.0 /)
>
> then It's not giving mean of the square grid box.
>
> It shows the something like that (given below), which is incorrect. So please let me know how can I get the square grid box mean and then extract as asciiwrite or print?
>
> (0) 23.76603307545667 75.53995171540016
> (0) 0.179
> (1) 0.142
> (2) -28672
> (3) 0.169
> (4) -28672
> (5) -28672
> (6) -28672
> (0) -----
> (0) 24.00322458681621 75.99551564353467
> (0) 0.171
> (1) 0.16
> (2) -28672
> (3) 0.17
> (4) -28672
> (5) -28672
> (6) -28672
>
> etc..etc..
>
>
>
> regards
> Kunal Bali
>
>
>
>
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Guido Cioni
http://guidocioni.altervista <http://guidocioni.altervista/>.org
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