Adding day-length function to the calculator?

[rdstern]

In analysing the sunshine data it would be good to include a function that calculates the daylength.

There are various R packages that have this. It is very simple with the geosphere package, and that looks potentially a useful package for us anyway, now we are more into mapping?

For example, with the Dodoma data just use geosphere::(-6.1630,Date) into a column called daylength and you are away!
The chillR package that we have already also has a daylength command, but that produces a list and seems more complicated to use.

Could we decide which package to use and then possibly add this to the dates keyboard in the calculator? It would be useful for the Pretoria workshop.