How to remove items in a vector from another vector

Question

I have two vectors:

a = c(1,1,2,2,3,3,4,4) 
b = c(1)

I want to remove the first match of b from a. Thus, here only the first 1 is removed from a:

c = c(1,2,2,3,3,4,4)

The order of items in a is not important.

I tried this code:

a[a != b]
a[! a %in% b] 

Both results are:

[1] 2 2 3 3 4 4.

All numbers of 1 are removed. However, I only want to remove the specific item in b from a.

If b = c(1, 1, 2), then I wish the result

[1] 2 3 3 4 4

a[-(1:3)]

The above code could lead to the result of [1] 2 3 3 4 4. However, I wish it could be more flexible. For example when the order of items are unknown or random:

a = c(3,4,3,1,2,2,1,4)

How can I do it using R?

Answer 1

vecsets package can perform standard set operations, while retaining duplicates:

vecsets::vsetdiff( c(1,1,2,2,3,3,4,4), c(1) )
## [1] 1 2 2 3 3 4 4

vecsets::vsetdiff( c(1,1,2,2,3,3,4,4), c(1,1,2) )
## [1] 2 3 3 4 4

Note that it will preserve the order of the first argument. Using your last example:

vecsets::vsetdiff( c(3,4,3,1,2,2,1,4), c(1,1,2) )
## [1] 3 4 3 2 4