`subset` doesn't work for arbitrary data additions

[lkilcher]

If you add a data-item that doesn't have a time-dimension that matches the other time dimensions, then subset won't work.

For now, a workaround is to pop the data item from the data object, then perform subset, then add it back:

z_ = dat.pop('z_')
dat2 = dat.subset[1000:5000]
dat2.z_ = z_
dat.z_ = z_

This is linked to the problem that we do not yet track the array dimensions. It looks like xarray has the functionality we need, perhaps we should switch to using that?

[lkilcher]

I just updated pyDictH5 so that the error message that is generated when this doesn't work is more informative. Update pyDictH5 to see these messages:

pip install git+https://github.com/lkilcher/pyDictH5

[mcfogarty]

The workaround works!
Including an example from my dataset as an FYI.

Pop the added data items from datETU

eta = datETU.pop('eta')  # Time series. Need to pop.
# mllw = datETU.pop('mllw') # Single value. No need to pop.
z_ = datETU.pop('z_') # One value per ADCP range bin. Need to pop.

# Subset the remaining datETU to crop time series from 100 days to 7 days.
trange = [start_time, end_time]
tinds = (trange[0] <= datETU.mpltime) & (datETU.mpltime <= trange[-1])
datETUsmb = datETU.subset[tinds]

# Put the data items back into both datETU and datETUsmb
datETU.eta = eta 
datETU.z_= z_

datETUsmb.eta = eta[tinds] 
datETUsmb.z_= z_ 

[lkilcher]

This issue is no longer relevant with the move to xarray as the dataset backend.