Database-style merge

[karosc]

I have a timeseries dataset I am trying to map a monthly pattern onto. I would normally achieve this in pandas by using pd.merge to achieve a database-style JOIN. I cannot figure out how to do this in xarray properly.

I have long timeseries Dataset with a time dim and a 12-value-long monthly pattern DataArray with a month dim. Can I do a database style of these two structures to get a new dataset with a new variable that has my monthly pattern mapped to each time in my long timeseries based on the its month?

[dcherian]

expanded = monthly.sel(month=ds.time.dt.month)?