How do I append new data to a new variable in a NETCDF file ?

I want to append new data to a new variable in the existing netcdf file and let other variables remain unchanged. However, when I use:

ncid=netcdf.open('E:\data\Landcover\MCD12Q1\heihe\surfdata_40x40_hh_gravtest.nc','WRITE'); 
gravid = netcdf.defVar(ncid,'PCT_GRAVEL','double',[40 40 10]); 

error shows:
Operation not allowed in data mode (NC_ENOTINDEFINE)

do you know how to solve it ? thanks

[dpb]

I "know (almost) nuthink!" per Sgt Schultz about NetCDF files, but the MATLAB interface supplies a higher-level abstracted function <nccreate> that purports to be able to do that. I'd suggest trying it.

If that fails, you'll have to dig a whole lot deeper into the file content of the file you have and the details of the required syntax/operations to add to it.

I dunno if .defVar is the first thing you can call or if you have to do more preliminary work first; it's a pretty complex format/system...

Answer 1

[Raghunathraju]

Hi,

As per my understanding, you want to append new data to a new variable in a NETCDF file.

You have used the following code to get your work done.

ncid=netcdf.open('E:\data\Landcover\MCD12Q1\heihe\surfdata_40x40_hh_gravtest.nc','WRITE'); 
gravid = netcdf.defVar(ncid,'PCT_GRAVEL','double',[40 40 10]); 

But the datatype you used in “netcdf.defVar” is double which is invalid for NETCDF .Instead you can use “NC_DOUBLE”.

For further reference you can go through the link below

https://www.mathworks.com/help/matlab/ref/netcdf.defvar.html?s_tid=doc_ta

[俊 马]

it didn't work... unless I use "ncid=netcdf.create...." instead of "ncid=netcdf.cpen...." but thanks