How do I use lappy to find means of a list of vectors while wanting to na.rm=TRUE

Question

So, Say I have

l <- list(a=c(1, 2, NA), b=c( 2, 3, NA), c=c(5, NA, 6))
lapply(l, mean)

How do I use lapply where I want the mean function to use the parameter na.rm=TRUE

The following is not working

lapply(l, mean(na.rm=TRUE))

Thanks.

Answer 1

Generally, you can use the ... to pass other arguments to your function, so the following should work:

l <- list(a=c(1, 2, NA), b=c( 2, 3, NA), c=c(5, NA, 6))
lapply(l, mean, na.rm = TRUE)

In some cases, it might be easier to use an anonymous function, like this:

lapply(l, function(x) mean(x, na.rm = TRUE))

---

In the second case above, that would be similar to doing something like:

1. Defining a new mean function preset with na.rm = TRUE :

    meanNArm <- function(x) mean(x, na.rm = TRUE) 

2. Using that function in lapply :

    lapply(l, meanNArm) 

If the function you were dealing with were quite complex, or if you had to do this regularly, then defining your own function might make sense, otherwise, a simple anonymous function (or passing the relevant argument with ... ) would be the more logical approach.