SUMIF rows equivalent in R

Question

I am looking to produce summary rows in R so that a table like this:

Region	Area	Numerator	Denominator
North	AreaA	1	10
North	AreaB	1	10
South	AreaC	1	10
South	AreaD	1	10

Becomes this:

Region	Numerator	Denominator
North	2	20
South	2	20

Very simple I'm sure for someone who understands the equivalent of SUMIF (Excel) for R. I have looked at other questions but am too new to R to figure this out. Any help very much appreciated.