R vector creation from data

In r I'm trying to figure out how to find which areas are contained in A, B, C,D, etc. For instance, A contains 540, 300, 330. While C contains area 330.

I would like to save these to a vector so like A = [540,300,330] and C = [300], and D = [540, 330]

Data:

Area    A   B   C   D
540     Y           Y    
300     Y       Y
330     Y           Y

I was thinking of using a summaryBy Statement. But this doesn't give me the desired outcome.

 summaryBy(Area ~ A, FUN=(length))