Count occurence of multiple numbers in vector one by one

Question

I have two vectors

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

I want to know how many times each element in b occur

Answer 1

You can do this using factor and table

table(factor(a, unique(b)))
#
#1 2 3 4 5 6
#3 3 2 1 2 0

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Since you mentioned match, here is a possibility without sapply loop (thanks to @thelatemail)

table(factor(match(a, b), unique(b)))
#
#1 2 3 4 5 6
#3 3 2 1 2 0