Create variables by running a function

<- or = for assignments?

Both assignments work:

x <- 6    will create a variable called x with value 6
x = 4     will change the value of variable x to 4

When R was developed only <- was used for assignments and = was used for logical operations: is x equal to 4? It’s confusing to use the same symbol for assignment and logical operations. If you do that then

x = 4    could mean: x is 4 but also is x 4? 

That is very messy.

Note that = was also used inside function calls to give values to arguments:

x <- mean(v, trim=0.1, na.rm=FALSE)

A lot of R users with programming experience hated the <- because all other programming languages use = for variable assignment. So R adopted both <- and = for assignment and started to use == for logical operations. They kept = inside function calls to give values to arguments since this is not confusing

x = 4
matrix(1:4,ncol=2,nrow=2)

The difference in meaning of = is clear here.

So now you can choose between <- and = for assignments. Old R programmers still prefer <- because it means you were already there in the beginning days of R and you’re cool while people who learned to program in another language before learning R prefer =