R lapply on list of dataframes resetting rownames

Question

You can reset the rownames in a data frame by running

>rownames(df) <- NULL

I have a list of dataframes and want to reset all the rownames on every dataframe in the list, I tried

>newlist <- llply(mylist, function(df) { rownames(df) <- NULL })

Bu tit doesn't work, returns a list of NULLS and the original remains unchanged.

Roland · Accepted Answer · 2013-06-05T11:09:24.820

9

This is a job for the base function lapply; you don't need to load plyr. You also need to make sure that your anonymous function returns something.

df1 <- data.frame(a=1:10)
rownames(df1) <- letters[1:10]

df2 <- data.frame(b=1:10)
rownames(df2) <- LETTERS[1:10]

mylist <- list(df1,df2)

mylist <- lapply(mylist,function(DF) {rownames(DF) <- NULL; DF})

edited Jun 05 '13 at 11:09

answered Jun 05 '13 at 11:01

Roland

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+1 If you wanted to be a little more concise you could write `lapply( mylist , \`rownames<-\` , NULL )` – Simon O'Hanlon Jun 05 '13 at 11:48

score 5 · Answer 2 · answered Jun 05 '13 at 12:05

5

Use rownames<- :

newlist <- lapply(mylist, "rownames<-", NULL)

answered Jun 05 '13 at 12:05

G. Grothendieck

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This doesn't seem any different (other than cosmetic) to Roland's answer or my subsequent comment under his answer. – Simon O'Hanlon Jun 05 '13 at 12:36
Hadn't noticed your comment. This one does use double quotes :) – G. Grothendieck Jun 05 '13 at 12:56

R lapply on list of dataframes resetting rownames

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