a b

1 30

1 10

1 8

2 10

2 18

2 5

I have this data-set with me, where column 'a' is of factor type with levels '1' and '2'. Column 'b' has random whole numbers. Now, i would want to filter this data-frame such that i only get values more than 15 from 'b' column where 'a=1' and get values greater 5 from 'b' where 'a==2'

So, i would want the output to be like this:

a b

1 30

2 10

2 18