[ncl-talk] Area average using shapefile
Mary Haley
haley at ucar.edu
Sun Mar 12 13:43:47 MDT 2017
I think you just need to conform your ts_mask array to be the same size as
your data array with the multiple timesteps.
First, create the mask using a single timestep of "ts". For example, if
"ts" is ntime x nlat x nlon:
ts_mask = mask_data_with_India_country(India_code,ts(0,:,:)) ;
arbitrarily chose time index=0
It shouldn't matter which timestep you choose, as long as your lat/lon grid
is the same for every time step.
Now, conform ts_mask to be the same size as ts:
ts_mask_3d = conform(ts,ts_mask,(/1,2/))
I think the rest of the code should work as expected.
--Mary
On Sat, Mar 11, 2017 at 4:51 PM, Ipshita Majhi <ipmajhi at alaska.edu> wrote:
> Dear NCL,
>
> I got the shapefile plot running thanks to Mary. I wanted to take an
> average of precipitaiton over India, if I run the code for one time step I
> am able to take an average but if I put try to do it for all the timesteps
> it gives me error.
>
> Is there a way to do the average for all the timestep?
> Can I save the created mask and then use it like I do with landsea.nc and
> use it for all diff precipitation dataset to get an average over India?
>
> Here is the code that I am using to take an average
>
> ;************************************************
> 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
> ;----------------------------------------------------------------------
> begin
> ;---Shapefile to use for masking. Using "Bolivia" here (BOL).
> 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.PRECSL.070001-079912.nc"
> f = addfile(filename,"r")
> ts = f->PRECSL
> printVarSummary(ts)
>
> ;---Mask "ts" against India shapefile outlines
> ts_mask = mask_data_with_India_country(India_code,ts)
> printVarSummary(ts_mask)
> ts_mask at _FillValue = -2.1474*10^9
> area_avg=wgt_areaave_Wrap(ts_mask,1,1,0)
> data_avg = wgt_areaave_Wrap((where(ts_mask.ge.0,ts_mask,ts at _FillValue)),1,1,0)
>
> printVarSummary(data_avg)
> print(data_avg)
>
>
>
>
> end
>
> --
> ************************************************************
> *******************************************************
> "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
>
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