On 2010-09-07 13:58, Cable, Samuel B Civ USAF AFMC AFRL/RVBXI wrote:
I would like to open an existing netCDF file and add a variable to it.
I am using the ncdf package. This test code gives the idea of what I am
trying to do:
library(ncdf)
print('here we go')
print('first, construct netCDF file')
t<-dim.def.ncdf('t','',1:1,unlim=T,create_dimvar=F)
print('defining first vars')
a<-var.def.ncdf('a','km',t,missval=-999)
b<-var.def.ncdf('b','km',t,missval=-999)
print('creating ncobj')
ncobj<-create.ncdf('testfile.nc',list(a,b))
print('adding data')
put.var.ncdf(ncobj,a,c(1,2,3,4,5),count=5)
put.var.ncdf(ncobj,b,c(10,20,30,40,50),count=5)
print('file constructed. close it.')
close(ncobj)
print('defining new var')
c<-var.def.ncdf('c','hrs',t,missval=-999)
print('now open file back up for adding variable')
ncobj<-open.ncdf('testfile.nc',write=T)
print('adding new var to ncobj')
ncnewer<-var.add.ncdf(ncobj,c)
print('new data')
put.var.ncdf(ncnewer,c,c(.1,.2,.3,.4,.5))
close.ncdf(ncnewer)
Everything works fine until the call to var.add.ncdf(), where R stops
with the very helpful error message "This is not allowed." Anybody see
what I am doing wrong? Note that I am indeed calling open.ncdf() with
write=T, as needed. Thanks.
Sam,
I haven't seen an answer to this yet.
I don't know much about netCDF, but the following seems to work.
The main thing is, I think, that you need to re-define your 't'
to be in line with what's in testfile.nc.
library(ncdf)
t <- dim.def.ncdf('t','',1:1,unlim=TRUE,create_dimvar=FALSE)
a <- var.def.ncdf('a','km',t,missval=-999)
b <- var.def.ncdf('b','km',t,missval=-999)
ncobj <- create.ncdf('testfile.nc',list(a,b))
put.var.ncdf(ncobj,a,c(1,2,3,4,5),count=5)
put.var.ncdf(ncobj,b,c(10,20,30,40,50),count=5)
close(ncobj)
ncobj <- open.ncdf('testfile.nc',write=TRUE)
t <- ncobj$dim[['t']]
c <- var.def.ncdf('c','hrs',t,missval=-999)
ncobj <- var.add.ncdf(ncobj,c)
close(ncobj)
tmp <- open.ncdf('testfile.nc',write=TRUE)
put.var.ncdf(tmp,c,c(.1,.2,.3,.4,.5))
close(tmp)
-Peter Ehlers
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