I have 2 frames, 1 has continent data, the other metals-group data.
continents
year africa asia
1996 2 3
1997 5 6
metal-groups
year ferrous non-ferrous
1996 2 3
1997 5 6
I need to merge them on 'year', and try keep the categories associated with the columns of the final frame (i.e. continents and metal-groups).
What's the best way to do this?