Recode numbers

I have two sets of numbers that look like

a<- c(1, 2, 3, 3, 4, 4, 5, 6, 1, 2, 2, 3, 1, 2, 1, 2, 3, 3, 4, 5, 1, 2, 3,
4)

b<- c(1, 5, 8, 9, 14, 20, 3, 10, 12, 6, 16, 7, 11, 13, 17, 18, 2, 4, 15,
19)

I just want to use ?b? to encode ?a? so that ?a? looks like

a1<- c(1, 5, 8, 8, 9, 9, 14, 20, 3, 10, 10, 12, 6, 16, 7, 11, 13, 13, 17,
18, 2, 4, 15, 19)

Does anyone have a suggestion how to deal with this? Thank you in advance.

is a1 = b[a] what you are looking for?

HTH

Pete

Thank you for your help, Pete. I tried b[a], but it is not a1.