Select rows from a data frame based on values in a vector

Have a look at ?"%in%".

dt[dt$fct %in% vc,]
   fct X
1    a 2
3    c 3
5    c 5
7    a 7
9    c 9
10   a 1
12   c 2
14   c 4

You could also use ?is.element:

dt[is.element(dt$fct, vc),]