$b
[1] 12

z$c <- "sailing" # add a c component

did c really get added?

z
$a
[1] "abc"

$b
[1] 12

$c
[1] "sailing"

Adding components can also be done via a vector index:

z[[4]] <- 28
z[5:7] <- c(FALSE,TRUE,TRUE)
z
$a
[1] "abc"

$b
[1] 12

$c
[1] "sailing"

[[4]]
[1] 28

[[5]]
[1] FALSE

[[6]]
[1] TRUE

[[7]]
[1] TRUE

You can delete a list component by setting it to NULL.

z$b <- NULL
z
$a
[1] "abc"

Lists 89