Plot labels - to determine variable names + units from the dataset

[eleanorfrajka]

Plots can take advantage of variable attributes for setting labels and units: Labels from long_name, and units from units. Might need some little utility to convert units to something pretty. E.g. 'm s-1' could be translated to 'm s$^{-1}$'. Although, I'm really not sure who decided "PSAL" would have units 1e-3. Ok, I read a little further through the vocabularies.py, and scratch that. long_name is not great "Temperature of the water body by CTD". Neither is standard_name "sea_water_pressure". Maybe somewhere we can set up a dictionary based on variable name and "plotting_name" or something.

BP700: My paper uses b${bp}$(700) for red backscatter (probably based on something by Sackmann or Mary-Jane Perry). Could be "Red backscatter, b${bp}$(700)"
PSAL: "Practical salinity"
TEMP: "Temperature"
SA: "Absolute salinity"
DENSITY: "In situ density"
DOXY: "Dissolved oxygen"
When the dictionary doesn't have a key for the variable the user wants to plot, then it can use just the varname.

Then the label_str = label_dict['BP700'] + utilities.nice_units(ds['BP700'].attrs['units'])
and the function (or widget) .nice_units() can translate from 'degrees_Celcius' to '$^\circ$C' and from 'm-1' to 'm$^{-1}$', etc.

• Plot labels - Initial function with basic variables #162
• Plot labels - Add all needed variables and units to dict
• Plot labels - Move dictionary outside utilities.py and have it as a separate json

[callumrollo]

I think this is a good idea. Having looked into it, this will require some changes to the functions that we have. We should pass xarray datasets and dataarrays with their corresponding metadata to/from functions like plot_updown_bias so that we can use the unit metadata and long/standard names to construct nice labels. This will also make the toolbox generally more interoperable and easier for the end user (no need to pass both the chlorophyll variable and the lable "chlorophyll a [mmol / litre]" to the plotting function

[MOchiara]

I am working on it but I am having a little doubt: in some case standard_name is better to use and in some other long_name is better.
Examples:

Eleanor already noticed this and we can have a plotting dictionary in utilities or something like that. What do you think? I can maybe prepare a draft