[ncl-talk] Area average while using shapefile

Ipshita Majhi ipmajhi at alaska.edu
Fri Mar 17 11:50:49 MDT 2017


Thank you Mary for the solving the issue. I am thankful and grateful

Best Regards
Ipshita

On Fri, Mar 17, 2017 at 7:07 AM, Mary Haley <haley at ucar.edu> wrote:

> Hi Ipshita,
>
> The "conform" function doesn't do the masking. It simply propagates a 2D
> array to a 3D array.
>
> You need to take this 2D mask array, conform it to 3D, and then apply it
> to your original "ts" data in order to "mask" the locations in "ts" where
> the values are 1:
>
> ;---Create a 2D mask array using India shapefile outlines
>   ts_mask_2d = mask_data_with_India_country(India_code,ts(0,:,:))
>
> ;---Conform this 2D array to a 3D array
>   ts_mask_3d = conform(ts,ts_mask_2d,(/1,2/))
>
> ;---Apply the 3D mask to "ts"
>   tm_3d = mask(ts,ts_mask_3d,1)    ; Keep ts when ts_mask_3d equal 1
>
>
> The tm_3d array should now be the one that you can average.
>
> By the way, there are some things you can do to clean up your code a
> little.
>
> [1] You don't need to use a "do" loop to calculate the average.  You can
> use "dim_avg_n" or "dim_avg_n_Wrap" (preserves metadata):
>
> prec_avg = dim_avg_n_Wrap(tm_3d,(/1,2/))
>
> [2] You generally don't ever need to use "new" unless you need to populate
> that array inside a do loop by indexing it, or you just need to create an
> empty array for some reason.
>
> So, you can replace this code:
>
>  precp_mon_avg = new((/100,12/),"float")
>
>  precp_mon_avg=reshape(prec_avg,(/100,12/))
>
> with just one line:
>
>  precp_mon_avg = reshape(prec_avg,(/100,12/))
>
> --Mary
>
>
> On Thu, Mar 16, 2017 at 1:48 PM, Ipshita Majhi <ipmajhi at alaska.edu> wrote:
>
>> Dear NCL Users,
>>
>> I am using shapefile to analyze data over India, thanks to Mary got the
>> shape file working and then also got the data conformed. But when I am
>> doing area average for each month the values are the same . I am not sure
>> what is going wrong. I am pasting my code in this email.
>>
>>
>> ;************************************************
>> load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/gsn_code.ncl"
>> load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/gsn_csm.ncl"
>> load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/contributed.ncl"
>> load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/shea_util.ncl"
>> ;************************************************
>> ;Read data to plot and mask
>> ;************************************************
>> function mask_data_with_India_country(country_code,data)
>> begin
>>
>> mask_start_time = get_cpu_time()     ; For timing results
>>
>> ;---Convert rectilinear grid to 2D grid, but laid out as 1D array.
>>   dims  = dimsizes(data)
>>   lat1d = ndtooned(conform_dims(dims,data&$data!0$,0))
>>   lon1d = ndtooned(conform_dims(dims,data&$data!1$,1))
>>
>>   shapefile_name = "IND_adm0.shx"
>>  ;---Open shapefile and read lat/lon values.
>>   sfilename = "IND_adm0.shp"
>>   f = addfile(sfilename,"r")
>>   segments = f->segments
>>   geometry = f->geometry
>>   segsDims = dimsizes(segments)
>>   geomDims = dimsizes(geometry)
>>
>> ;---Read global attributes
>>   geom_segIndex = f at geom_segIndex
>>   geom_numSegs  = f at geom_numSegs
>>   segs_xyzIndex = f at segs_xyzIndex
>>   segs_numPnts  = f at segs_numPnts
>>   numFeatures   = geomDims(0)
>>
>>   lon  = f->x
>>   lat  = f->y
>>   nlatlon = dimsizes(lat)
>>
>>   min_lat = min(lat)
>>   max_lat = max(lat)
>>   min_lon = min(lon)
>>   max_lon = max(lon)
>>
>>   print("==================================================")
>>   print("Shapefile : "  + sfilename)
>>   print("min_lat " + min_lat)
>>   print("max_lat " + max_lat)
>>   print("min_lon " + min_lon)
>>   print("max_lon " + max_lon)
>>
>>    ii_latlon = ind(min_lat.le.lat1d.and.lat1d.le.max_lat.and.\
>>                   min_lon.le.lon1d.and.lon1d.le.max_lon)
>>   nii = dimsizes(ii_latlon)
>>   print(nii + " values to check")
>>   print(numFeatures + " feature(s) to traverse with a maximum of " + \
>>         nlatlon + " points")
>>
>>
>>  ;---Create array to hold new data mask, and set all values to 0
>> initially.
>>   data_mask_1d = new(dimsizes(lat1d),integer)
>>   data_mask_1d = 0
>>
>> ;
>> ; This is the loop that checks every point in lat1d/lon1d to see if it
>> ; is inside or outside of the country. If it is inside, then data_mask_1d
>> ; will be set to 1.
>> ;
>>   ikeep = 0    ; Counter to see how many points were found inside the
>> country
>>   do n=0,nii-1
>>     ii = ii_latlon(n)
>>     is_inside = False
>>     i = 0
>>     do while(.not.is_inside.and.i.lt.numFeatures)
>>        startSegment = geometry(i, geom_segIndex)
>>        numSegments  = geometry(i, geom_numSegs)
>>        do seg=startSegment, startSegment+numSegments-1
>>          startPT = segments(seg, segs_xyzIndex)
>>          endPT   = startPT + segments(seg, segs_numPnts) - 1
>>          if(data_mask_1d(ii).ne.1.and.\
>>             gc_inout(lat1d(ii),lon1d(ii),\
>>                      lat(startPT:endPT),lon(startPT:endPT))) then
>>            data_mask_1d(ii) = 1
>>            ikeep = ikeep+1
>>            is_inside = True
>>            continue
>>          end if
>>        end do
>>        i = i + 1
>>     end do
>>   end do
>>   print(ikeep + " values kept")
>>   print("==================================================")
>>
>> ; Create a 2D data array of same size as original data,
>> ; but with appropriate values masked.
>> ;
>>   data_mask = (where(onedtond(data_mask_1d,dims).eq.1,data,\
>>               data at _FillValue))
>>   copy_VarMeta(data,data_mask)      ; Copy all metadata
>>
>> ;---Print timings
>>   mask_end_time = get_cpu_time()
>>   print("Elapsed time in CPU second for 'mask_data_with_India_country' =
>> " + \
>>          (mask_end_time-mask_start_time))
>>
>>   return(data_mask)
>> end
>>
>> ;----------------------------------------------------------------------
>> ; Main code
>> ;----------------------------------------------------------------------
>>
>> ;---Shapefile to use for masking. Using India (IND)
>> India_code = "IND"
>> India_name = "IND" + "_adm0"
>> India_shp  = "IND_adm0.shp"
>>
>> ;---Read lat/lon off shapefile
>>  s         = addfile(India_shp,"r")
>>  slat      = s->y
>>  slon      = s->x
>>
>> ;---Read precipitation data to contour and mask
>>   filename = "b.e11.B1850C5CN.f09_g16.005.cam.h0.PRECC.070001-079912.nc"
>>   f        =  addfile(filename,"r")
>>   ts       = f->PRECC(:,:,:)
>>
>>
>> ;---Mask "ts" against India shapefile outlines
>>   ts_mask = mask_data_with_India_country(India_code,ts(0,:,:))
>>   tm_3d=conform(ts,ts_mask,(/1,2/))
>>
>>
>>
>>   tm_3d at _FillValue = ts at _FillValue
>>
>> ;  copy_VarAtts(ts,tm_3d)
>>   copy_VarCoords(ts,tm_3d)
>>
>>  print(tm_3d(100,{25},{70}))
>>  print(tm_3d(110,{25},{74}))
>>
>>  printVarSummary(tm_3d)
>>  printMinMax(tm_3d, True)
>>
>>  prec_avg = new((/1200/),"float")
>>
>>  do ii =0,1199
>>
>>  prec_avg(ii) = avg(tm_3d(ii,:,:))
>>
>>  end do
>>
>>  precp_mon_avg = new((/100,12/),"float")
>>
>>  precp_mon_avg=reshape(prec_avg,(/100,12/))
>>
>>
>>  precp_mon = dim_avg_n(precp_mon_avg,0)
>>
>>  print(precp_mon)
>>
>>
>>
>>
>>
>>
>>
>>
>> --
>> ************************************************************
>> *******************************************************
>> "I slept and dreamt that life was joy. I awoke and saw that life was
>> service. I acted and behold, service was joy." - Rabindranath Tagore
>> ************************************************************
>> ********************************************************
>>
>> Ipshita Majhi
>> PhD Candidate
>> University of Alaska , Fairbanks
>> Atmospheric Science Department
>> (907)978-4220 <(907)%20978-4220> ipmajhi at alaska.edu
>>
>> _______________________________________________
>> ncl-talk mailing list
>> ncl-talk at ucar.edu
>> List instructions, subscriber options, unsubscribe:
>> http://mailman.ucar.edu/mailman/listinfo/ncl-talk
>>
>>
>


-- 
*******************************************************************************************************************
"I slept and dreamt that life was joy. I awoke and saw that life was
service. I acted and behold, service was joy." - Rabindranath Tagore
********************************************************************************************************************

Ipshita Majhi
PhD Candidate
University of Alaska , Fairbanks
Atmospheric Science Department
(907)978-4220 ipmajhi at alaska.edu
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://mailman.ucar.edu/pipermail/ncl-talk/attachments/20170317/c5787e8c/attachment.html 


More information about the ncl-talk mailing list