Applying a function to multiple data frames

Question

I've written a simple code to add two columns (A_Purchase_Freq and T_A_Expenditure) to my dataset WM_Purchased_1:

WM_Purchased_1 <- WM_Purchased_1 %>% 
    mutate(A_Purchase_Freq = 
            ifelse(utfoodb=="Daily", tfoodb*30*mfoodbly, 
            ifelse(utfoodb=="Weekly", tfoodb*4*mfoodbly,
            ifelse(utfoodb=="Monthly", tfoodb*1*mfoodbly,
            ifelse(utfoodb=="Quarterly", tfoodb*4, 
            ifelse(utfoodb=="Bi-Annually", tfoodb*2,
            ifelse(utfoodb=="Annually", tfoodb*1, "NA"))))))) %>%
    mutate(A_Purchase_Freq= as.numeric(A_Purchase_Freq)) %>%
    mutate(T_A_Expenditure = A_Purchase_Freq * cfoodb)

I'd now like to apply the same function to 3 more datasets (WM_Purchased_2, WM_Purchased_3, WM_Purchased_4).

So far, I've created the function f1:

  f1 <- function(dat) {
    dat<- dat %>% 
        mutate(A_Purchase_Freq = 
                ifelse(utfoodb=="Daily", tfoodb*30*mfoodbly, 
                ifelse(utfoodb=="Weekly", tfoodb*4*mfoodbly,
                ifelse(utfoodb=="Monthly", tfoodb*1*mfoodbly,
                ifelse(utfoodb=="Quarterly", tfoodb*4, 
                ifelse(utfoodb=="Bi-Annually", tfoodb*2,
                ifelse(utfoodb=="Annually", tfoodb*1, "NA"))))))) %>%
        mutate(A_Purchase_Freq= as.numeric(A_Purchase_Freq)) %>%
        mutate(T_A_Expenditure = A_Purchase_Freq * cfoodb) 
  }

I then created a list of my data frames using list(), and attempted to apply my function to the list use lapply:

  dflist<- list(WM_Purchased_2, WM_Purchased_3, WM_Purchased_4)
  lapply(dflist, f1)

But I can't for the life of me figure out how to add the columns to the original data frames, rather than just returning the data in the console or as a list.

Any help would be appreciated! (Sorry I can't share the datasets)

Edit: Here's a reproducible example:

    m1 <- as.data.frame(matrix(1:12, 3, 4, dimnames=list(LETTERS[1:3], LETTERS[1:4])))
    m2 <- as.data.frame(matrix(4:15, 3, 4, dimnames=list(LETTERS[1:3], LETTERS[1:4])))
    
    listdf<- list(m1, m2)
    f1 <- function(dat) {
      dat<- dat %>% 
        mutate(E = C* D)
    }
    
    lapply(listdf, f1)

So in short I want column E added to data frames m1 and m2, not returned in the console.

It would help if you made this a **minimal** reproducible example. Although you state you cant share the data, making a reproducible example does not have to use your real data (and often dent). See [here](https://stackoverflow.com/questions/5963269/how-to-make-a-great-r-reproducible-example) for some tips — jpsmith, Mar 17 '23 at 18:16

asd-tm · Answer 1 · 2023-03-20T13:13:01.573

You just need to return dat in your function declaration:

f1 <- function(dat) {
    dat<- dat %>% 
        mutate(A_Purchase_Freq = 
                ifelse(utfoodb=="Daily", tfoodb*30*mfoodbly, 
                ifelse(utfoodb=="Weekly", tfoodb*4*mfoodbly,
                ifelse(utfoodb=="Monthly", tfoodb*1*mfoodbly,
                ifelse(utfoodb=="Quarterly", tfoodb*4, 
                ifelse(utfoodb=="Bi-Annually", tfoodb*2,
                ifelse(utfoodb=="Annually", tfoodb*1, "NA"))))))) %>%
        mutate(A_Purchase_Freq= as.numeric(A_Purchase_Freq)) %>%
        mutate(T_A_Expenditure = A_Purchase_Freq * cfoodb) 
     dat
  }

Or remove assignment:

f1 <- function(dat) {
        dat %>% 
        mutate(A_Purchase_Freq = 
                ifelse(utfoodb=="Daily", tfoodb*30*mfoodbly, 
                ifelse(utfoodb=="Weekly", tfoodb*4*mfoodbly,
                ifelse(utfoodb=="Monthly", tfoodb*1*mfoodbly,
                ifelse(utfoodb=="Quarterly", tfoodb*4, 
                ifelse(utfoodb=="Bi-Annually", tfoodb*2,
                ifelse(utfoodb=="Annually", tfoodb*1, "NA"))))))) %>%
        mutate(A_Purchase_Freq= as.numeric(A_Purchase_Freq)) %>%
        mutate(T_A_Expenditure = A_Purchase_Freq * cfoodb) 
  }

APPENDED

To have the result of lapply() stored you need to simply assign the returned value to any new or existing variable. For instance:

dflist <- lapply(dflist, f1)

Thre result of lapply() will not be output to console but stored in the provided variable.

Thanks for your reply! Unfortunately I'm still getting the same result, the data is returning in the console with the new columns added but they're not being added to the original data sets. — Anna, Mar 20 '23 at 10:23

Applying a function to multiple data frames

1 Answers1