using lapply on a list of dataframes

Question

I created a list of dataframes called "list" and want to select only certain columns of every dataset in the list.

library(dplyr)
new_list <- lapply(list, select(list, Date))

It returns an error because class(list[1]) is not dataframe but still a list. class(list[[1]]) is dataframe. I don't understand that because the elements in my list should be dataframes and I also don't know how I can use "lapply" anyway.

Thanks for your help!

Answer 1

I think your syntax is just a little off. Try using an anonymous function instead:

l <- list(mtcars,mtcars)
lapply(l,function(x) select(x,cyl,mpg))

Answer 2

另外要记住[本身是一个函数，因此：

new_list <- lapply(list, '[', c("list", "Date"))