[R-sig-Geo] Extract spatial mean of subset of netCDF.

[Aseem Sharma]

Hi,

I am  new with raster work in R.

I am trying to get the spatial mean of a subset (define by the extent) of
larger domain netCDF data file using raster and ncdf packages

The netCDF data of Snow Water Equivalent(SWE) were obtained from
http://www.globsnow.info/swe/archive_v2.0/. The two files I have used are
nc1
<https://www.dropbox.com/s/tk388w67tjg704s/GlobSnow_SWE_L3A_19900101_v2.0.nc?dl=0>
and nc2
<https://www.dropbox.com/s/pft2dlio96n6ncw/GlobSnow_SWE_L3A_19900102_v2.0.nc?dl=0>
.

The codes I used are

library(raster)

library(ncdf)

nc1<-"C:\\Users\\bunug_000.BUNU\\Documents\\Dropbox\\Public\\
GlobSnow_SWE_L3A_19900101_v2.0.nc"

nc2<-"C:\\Users\\bunug_000.BUNU\\Documents\\Dropbox\\Public\\
GlobSnow_SWE_L3A_19900102_v2.0.nc"



about_nc<-open.ncdf(nc1)

print(about_nc)



nc_data<-stack(nc1,nc2,varname="SWE")

print(nc_data)

dim(nc_data)

nc_data1<-brick(nc_data)

plot(nc_data1)

subsetd<-extent(-78,-74,50,52)

subsetd

crop_data <- crop(nc_data1, subsetd)

dim(dt.ras.c)



dt.anm<-as.data.frame(cbind(unname(cellStats(dt.ras.c,
stat="mean")),seq(1:2))) # use unname to separate named numebr to just
numbers

str(dt.anm)

colnames(dt.anm)<-c("Mean_SWE","ID")


What is not right here so that I am not getting mean SWE. It should not be
-1.

Any suggestions will be highly appreciated.

Thank you.


------------------

"Namaste नमस्ते"

Aseem Sharma

Graduate Research Assistant

Northern Hydrometeorology Group(NHG)

Natural Resources and Environmental Studies Institute(NRESi)

University of Northern British Columbia

Prince George, BC, V2N 4Z9, Canada

Tel: 250-960-5427

Web: http://www.unbc.ca/


 "All know the Way, but few actually walk it."
"सबैको कल्याण होस् ।"

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