(R) How to tell what is in one vector and not another?

Question

In matlab there is a way to find the values in one vector but not in the other.

for example:

x <- c(1,2,3,4)
y <- c(2,3,4)

is there any function that would tell me that the value in x that's not in y is 1?

Answer 1

Yes. For vectors you can simply use the %in% operator or is.element() function.

> x[!(x %in% y)]
1

For a matrix, there are many difference approaches. merge() is probably the most straight forward. I suggest looking at this question for that scenario.

Answer 2

you can use the setdiff() (set difference) function:

> setdiff(x, y)
[1] 1

Answer 3

The help file in R for setdiff, union, intersect, setequal, and is.element provides information on the standard set functions in R.

Answer 4

x[is.na(match(x,y))]