Question

I’m trying to learn about loops and I currently have a long list of data frames and I need to go inside a bunch of these data frames and rename some variables. I have a function, but I’m struggling to construct a smart way to loop thru my list (the real list is much longer than in the example below) and at the same time apply varying suffixes prefixes hen renaming.

Hopefully my working example below will illustrate the situation. I imagine I can build the last part into two loops, but I can’t seem to figure out how I write to the data frame inside the list inside a loop.

Any help would be appreciated!

data(mtcars)

mtcarsList <- list(mtcars1 = mtcars, mtcars2 = mtcars,
                   mtcarsA = mtcars, mtcars = mtcars  )

# function I use to renames a specific number of variables
baRadd <- function(df, vector, suffix){
               names(df) <- ifelse(names(df) %in% vector,names(df), 
                                  paste(suffix, names(df), sep = ".")) 
               return(df)}


foo <- c("mpg", "cyl", "disp")
suffix1 <- "bar"
suffix2 <- "barBAR"
suffix3 <- "barBARbar"

mtcarsList$mtcars1 <- baRadd(mtcarsList$mtcars1, foo, suffix1)
mtcarsList$mtcars2 <- baRadd(mtcarsList$mtcars2, foo, suffix2)
mtcarsList$mtcarsA <- baRadd(mtcarsList$mtcarsA, foo, suffix3) 

 names(mtcarsList$mtcars1)
 # [1] "mpg"      "cyl"      "disp"     "bar.hp"   "bar.drat" "bar.wt"  
 # [7] "bar.qsec" "bar.vs"   "bar.am"   "bar.gear" "bar.carb"
 names(mtcarsList$mtcars2)
 # [1] "mpg"         "cyl"         "disp"        "barBAR.hp"   "barBAR.drat"
 # [6] "barBAR.wt"   "barBAR.qsec" "barBAR.vs"   "barBAR.am"   "barBAR.gear"
 # [11] "barBAR.carb"
 names(mtcarsList$mtcarsA)
 # [1] "mpg"            "cyl"            "disp"           "barBARbar.hp"  
 # [5] "barBARbar.drat" "barBARbar.wt"   "barBARbar.qsec" "barBARbar.vs"  
 # [9] "barBARbar.am"   "barBARbar.gear" "barBARbar.carb"
 names(mtcarsList$mtcars)
 # [1] "mpg"  "cyl"  "disp" "hp"   "drat" "wt"   "qsec" "vs"   "am"   "gear"
 # [11] "carb"

Update,

Based on DWin’s response below I write this scrip that solves my issue,

# rm(list = ls(all = TRUE)) ## Clear workspace

data(mtcars)

mtcarsList <- list(mtcars1 = mtcars, mtcars2 = mtcars, 
                    mtcarsA = mtcars, mtcars = mtcars)

## function I use to renames a specific number of variables
baRadd <- function(df, vector, suffix){
               names(df) <- ifelse(names(df) %in% vector,names(df), 
                                  paste(suffix, names(df), sep = ".")) 
               return(df)}


suffixes <- c('A', 'B', 'C') # suffixes to be added to the three dfTO
whatNOTtoRename <- c("mpg", "cyl", "disp") 
# variables within the data frame I do not     want to renames
dfTO <- c('mtcars1','mtcars2','mtcarsA') 
# the specific data frames I need to rename


# str(mtcarsList)
mtcarsList[ names( mtcarsList[dfTO]) ] <- 
     mapply(baRadd, df=mtcarsList[dfTO], 
                    suffix= suffixes, 
                    MoreArgs=list(vector=whatNOTtoRename) , SIMPLIFY=FALSE)

str(mtcarsList)

Answer 1

Looks as though mapply can do this task:

> newList <- mapply(baRadd, df=mtcarsList[1:3], suffix= c(suffix1, suffix2, suffix3), MoreArgs=list(vector=foo) , SIMPLIFY=FALSE)
> str(newList)
List of 3
 $ mtcars1:'data.frame':    32 obs. of  11 variables:
  ..$ mpg     : num [1:32] 21 21 22.8 21.4 18.7 18.1 14.3 24.4 22.8 19.2 ...
  ..$ cyl     : num [1:32] 6 6 4 6 8 6 8 4 4 6 ...
  ..$ disp    : num [1:32] 160 160 108 258 360 ...
  ..$ bar.hp  : num [1:32] 110 110 93 110 175 105 245 62 95 123 ...
  ..$ bar.drat: num [1:32] 3.9 3.9 3.85 3.08 3.15 2.76 3.21 3.69 3.92 3.92 ...
  ..$ bar.wt  : num [1:32] 2.62 2.88 2.32 3.21 3.44 ...
  ..$ bar.qsec: num [1:32] 16.5 17 18.6 19.4 17 ...
  ..$ bar.vs  : num [1:32] 0 0 1 1 0 1 0 1 1 1 ...
  ..$ bar.am  : num [1:32] 1 1 1 0 0 0 0 0 0 0 ...
  ..$ bar.gear: num [1:32] 4 4 4 3 3 3 3 4 4 4 ...
  ..$ bar.carb: num [1:32] 4 4 1 1 2 1 4 2 2 4 ...
 $ mtcars2:'data.frame':    32 obs. of  11 variables:
  ..$ mpg        : num [1:32] 21 21 22.8 21.4 18.7 18.1 14.3 24.4 22.8 19.2 ...
  ..$ cyl        : num [1:32] 6 6 4 6 8 6 8 4 4 6 ...
  ..$ disp       : num [1:32] 160 160 108 258 360 ...
  ..$ barBAR.hp  : num [1:32] 110 110 93 110 175 105 245 62 95 123 ...
  ..$ barBAR.drat: num [1:32] 3.9 3.9 3.85 3.08 3.15 2.76 3.21 3.69 3.92 3.92 ...
  ..$ barBAR.wt  : num [1:32] 2.62 2.88 2.32 3.21 3.44 ...
  ..$ barBAR.qsec: num [1:32] 16.5 17 18.6 19.4 17 ...
  ..$ barBAR.vs  : num [1:32] 0 0 1 1 0 1 0 1 1 1 ...
  ..$ barBAR.am  : num [1:32] 1 1 1 0 0 0 0 0 0 0 ...
  ..$ barBAR.gear: num [1:32] 4 4 4 3 3 3 3 4 4 4 ...
  ..$ barBAR.carb: num [1:32] 4 4 1 1 2 1 4 2 2 4 ...
 $ mtcarsA:'data.frame':    32 obs. of  11 variables:
  ..$ mpg           : num [1:32] 21 21 22.8 21.4 18.7 18.1 14.3 24.4 22.8 19.2 ...
  ..$ cyl           : num [1:32] 6 6 4 6 8 6 8 4 4 6 ...
  ..$ disp          : num [1:32] 160 160 108 258 360 ...
  ..$ barBARbar.hp  : num [1:32] 110 110 93 110 175 105 245 62 95 123 ...
  ..$ barBARbar.drat: num [1:32] 3.9 3.9 3.85 3.08 3.15 2.76 3.21 3.69 3.92 3.92 ...
  ..$ barBARbar.wt  : num [1:32] 2.62 2.88 2.32 3.21 3.44 ...
  ..$ barBARbar.qsec: num [1:32] 16.5 17 18.6 19.4 17 ...
  ..$ barBARbar.vs  : num [1:32] 0 0 1 1 0 1 0 1 1 1 ...
  ..$ barBARbar.am  : num [1:32] 1 1 1 0 0 0 0 0 0 0 ...
  ..$ barBARbar.gear: num [1:32] 4 4 4 3 3 3 3 4 4 4 ...
  ..$ barBARbar.carb: num [1:32] 4 4 1 1 2 1 4 2 2 4 ...

If you wanted to assign that result to mtcarsList[1:3], that too should be possible.

To your comment: this succeeds ….

mtcarsList[ names( mtcarsList[1:3]) ] <- 
         mapply(baRadd, df=mtcarsList[1:3], 
                        suffix= c(suffix1, suffix2, suffix3), 
                        MoreArgs=list(vector=foo) , SIMPLIFY=FALSE)

 # omitted output of str(mtcarsList)  ....