input data table. This has to contain the observations for the year to plot, as well as for many other years (which are used to calculate the climatological reference).
The data table should have coumns named lon
, lat
, year
, and an observation column, the name of which is passed as value of o
to the function, see below.
For each level of lon
, lat
, and year
, the table should only contain one row (this is checked by the function).