Altering the column names of dataframes in a list with lapply-CodePudding

I want to add a prefix to the colnames of dataframes in a list, based on the name of the dataframe:

list1 <- vector("list", 6)

list1 <- lapply(list1, function(x) data.frame(replicate(10,sample(0:1,10,rep=TRUE))))
list1 <- lapply(list1, function(x) {colnames(x)<- letters[1:10];x})
names(list1) <- LETTERS[1:6]

At this point, i want to change the colnames with something like:

    colnames(list1[[1]]) <- paste(names(list1[1]), colnames(list1[[1]]), sep=".")
    colnames(list1[[1]])
    [1] "A.a" "A.b" "A.c" "A.d" "A.e" "A.f" "A.g" "A.h" "A.i" "A.j"

How can i do this sequentally on each of the six dataframes? I tried

lapply(list1, function(x) {colnames(list1[x]) <- paste(names(list1[x]), colnames(list1[[x]]), sep=".");x })

but

Error in list1[x] : invalid subscript type 'list'

I guess its about cycling through the names of list1? Or how is it done?

Thanks for your help.

CodePudding user response：

Using base R, you can use Map.

Map(function(x, y) setNames(x, paste(names(x), y, sep = ".")), list1, names(list1))

Here is another way using purrr. The i functions (e.g., imap, imodify) will pass the name of the list item in as parameter .y along with the list contents in .x.

library(purrr)

imodify(list1, ~ set_names(.x, paste(names(.x), .y, sep = ".")))

CodePudding user response：

another way, if you have your dataframes already prepared and want to prefix columns with each dataframe's name:

## example dataframes
df1 <- data.frame(col1 = runif(1))
df2 <- data.frame(col1 = runif(1))

library(purrr)

dataframes_to_change = c('df1','df2')

walk(dataframes_to_change, ~{
    df <- get(.x)
    names(df) <- paste(.x, names(df), sep = '_')
    assign(.x, value = df, pos = 1)
})

CodePudding user response：

Modifying attributes might be faster.

Map(`attr<-`, list1, 'names', Map(paste, names(list1), lapply(list1, attr, 'names'), sep='.'))