Ken,
You could make lat, lon etc. netcdf dimensions by having variables
called lat, lon etc. and defining values for them. E.g., lat(lat) =
(30., 40., 50., ...), so a variable 'lat' that has the length 'lat' and
the values of latitude inside. However, you won't be able to slice with
standard tools unless your data array actually uses that dimension as
one of the dimensions. And given the nature of your data, I don't see
how that's possible. It seems like you're trying to subset from the
command line, i.e., "which points have lat between L1 and L2?" I don't
know if there's an NCO tool that does that, maybe someone else has a
better idea.
Any reason why you're making lon, lat and ID strings? They're all
numbers, no?
-Sourish
On 3/18/19 4:50 PM, Ken Mankoff wrote:
> Hi Sourish, Gus, and Elizabeth,
>
> Thank you all for your suggestions. I think I've found something that works,
> except for one issue. Please excuse my likely incorrect use of terminology -
> being new to NetCDF creation I may say something incorrect, but I hope the
> data dump below speaks for itself.
>
> Because my data is 2D (time, ID), then those are the dimensions, and
> lon,lat,x,y become variables on the ID dimension. This means my standard
> netcdf tools for slicing based on spatial dimension don't work. For example,
>
> cdo sellonlatbox,83.5,85,-27,-28 ds.nc bar.nc
>
> or
>
> ncks -d lat,83.5,85 -d lon,-27,-28 ds.nc bar.nc
> # ncks: ERROR dimension lat is not in input file
>
> Is there a way to make the data 2D but have the 2nd dimension be (lon,lat)?
> Even if yes, I don't imagine the cdo and ncks tools would work on that
> dimension... Is there a cdo, nco, or ncks (or other) simple tool I'm missing
> that can work with this non-gridded data the way those tools do so easily
> work with gridded data?
>
>
> Anway, here is the Python xarray code I got working to produce the NetCDF
> file, reading in the 'foo.csv' from my previous email and generating ds.nc.
> Once I understood the NetCDF structure from the file Sourish provided, I was
> able to generate something similar using a higher level API - one that takes
> care of time units, calendar, etc. I leave out (x,y,elev) for brevity.
>
>
> -k.
>
>
>
> df = pd.read_csv('foo.csv', index_col=0, header=[0,1,2,3,4,5])
> df.index = pd.to_datetime(df.index)
>
> # Build the dataset
> ds = xr.Dataset()
> ds['lon'] = (('ID'), df.columns.get_level_values('lon'))
> ds['lat'] = (('ID'), df.columns.get_level_values('lat'))
> ds['runoff'] = (('time', 'ID'), df.values)
> ds['ID'] = df.columns.get_level_values('ID')
> ds['time'] = df.index
>
> # Add metadata
> ds['lon'].attrs['units'] = 'Degrees East'
> ds['lon'].attrs['long_name'] = 'Longitude'
> ds['lat'].attrs['units'] = 'Degrees North'
> ds['lat'].attrs['long_name'] = 'Latitude'
> ds['runoff'].attrs['units'] = 'm^3/day'
> ds['ID'].attrs['long_name'] = 'Basin ID'
>
> ds.to_netcdf('ds.nc')
>
>
>
>
> And here is the ncdump of the file
>
>
>
>
>
> netcdf ds {
> dimensions:
> ID = 10 ;
> time = 5 ;
> variables:
> string lon(ID) ;
> lon:units = "Degrees East" ;
> lon:long_name = "Longitude" ;
> string lat(ID) ;
> lat:units = "Degrees North" ;
> lat:long_name = "Latitude" ;
> double runoff(time, ID) ;
> runoff:_FillValue = NaN ;
> runoff:units = "m^3/day" ;
> runoff:long_name = "RACMO runoff" ;
> string ID(ID) ;
> ID:long_name = "Basin ID" ;
> int64 time(time) ;
> time:units = "days since 1980-01-01 00:00:00" ;
> time:calendar = "proleptic_gregorian" ;
>
> // global attributes:
> :Creator = "Ken Mankoff" ;
> :Contact = "kdm@xxxxxxx" ;
> :Institution = "GEUS" ;
> :Version = 0.1 ;
> data:
>
> lon = "-27.983", "-27.927", "-27.894", "-28.065", "-28.093", "-28.106",
> "-28.155", "-27.807", "-27.455", "-27.914" ;
>
> lat = "83.505", "83.503", "83.501", "83.502", "83.501", "83.499", "83.498",
> "83.485", "83.471", "83.485" ;
>
> runoff =
> 0.023, 0.01, 0.023, 0.005, 0, 0, 0, 0, 0, 0,
> 0.023, 0.01, 0.023, 0.005, 0, 0, 0, 0, 0, 0,
> 0.024, 0.013, 0.023, 0.005, 0, 0, 0, 0, 0, 0,
> 0.025, 0.012, 0.023, 0.005, 0, 42, 0, 0, 0, 0,
> 0.023, 0.005, 0.023, 0.005, 0, 0, 0, 0, 0, 0 ;
>
> ID = "1", "2", "5", "8", "9", "10", "12", "13", "15", "16" ;
>
> time = 0, 1, 2, 3, 4 ;
> }
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