Non duplicate remove subsetting

Question

The below are by 'a' and 'b':

a <- c("A", "B", "C", "A", "A", "B")

b <- c("A", "C", "A")

I wanted to subset 'a' with respect to 'b' so that I can get the following set of values:

("B"  "A"  "B")

So what I want is while performing the subset of 'a' with respect to 'b' only two "A"s and one "C" should be removed from set a. And all of the rest of the elements that are in 'a' should remain even though they might be "A" or "C".

Answer 1

You can follow the below code, that may help you to reach  your target output:

#Count occurrences of `a`

a_count <- table(a)

#Count occurrences of `b`

b_count <- table(b)

#Subtract the count present in b from a 

a_count[names(b_count)] <- a_count[names(b_count)] - b_count

#Create a new vector of remaining values 

rep(names(a_count), a_count)

#[1] "A" "B" "B"

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