R - avoiding loops with nested lists

Question

I know that for loops can be avoided almost all the time in R if you understand the language properly, but I'm struggling to find out the clever way of doing this

for (i in 1:100){
  AllData[[i]]$Div = NULL
}

Where AllData is a list of 100 lists of various sizes. Can someone clue me in?

flodel · Accepted Answer · 2012-09-23 10:25:32Z

5

Like this:

AllData <- lapply(AllData, `[[<-`, "Div", NULL)

edited Sep 23, 2012 at 10:25

answered Sep 23, 2012 at 10:18

flodel

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8 Comments

N. McA. Over a year ago

Isn't it possible without lapply?

flodel Over a year ago

What's wrong with it? It seems appropriate since you are working with a list.

N. McA. Over a year ago

There's nothing wrong, but it doesn't really further my understanding that much because it's so equivalent to my code. I might be looking for something that doesn't exist though, as I was expecting something like AllData[[1:100]] = NULL

flodel Over a year ago

I don't think you can, but let's wait and see. Also note that your AllData[[1:100]] = NULL does not mention Div.

John Over a year ago

There is no increase in readability with a for loop unless you cannot read R. A big purpose of apply is expressiveness and avoiding the typical tendency to write long for loops. Just thinking of doing each step separately with a separate apply often provides performance boosts because somewhere in there you can get in a vectorized operation.

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