I would like to merge 2 data frames additively such that
taxonomy A B C
1 rat 0 1 2
2 dog 1 2 3
3 cat 2 3 0
and
taxonomy A D C
1 rat 0 1 9
2 Horse 0 2 6
3 cat 2 0 2
produce
taxonomy A B C D
1 rat 0 1 11 1
2 Horse 0 0 6 2
3 cat 4 3 2 0
4 dog 1 2 3 0
I've tried aggregate, merge, apply, ddply.... with no success...this will be done on 2 data frames with a couple hundred rows and columns