Using lapply with an R function that selects a column of data.frame

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I have a function that takes a column p of a data.frame dat and sums the similar values:

response <- function(dat, p){
    y = dat[p]
    sums = table(y)
    sums_df = as.data.frame(sums)
    #sums_df$rfreq = (sums_df$Freq/sum(sums_df$Freq))*100
    #sums_df$rfreq = round(sums_df$rfreq, digits = 0)
    #sums_df = sums_df[1:4, c(1,3)]
  return(sums_df)  
}

This works fine when run individually.

> response(SOM_C, "f76a")
  f76a Freq
1    1    5
2    2   51
3    3   14
4    4    6
5    5   29
6   97    1
7   99    7

But when I try to run it with through a list of separate data.frames (which include 'SOM_C')

plist <- c(SOM_V, SOM_SD, SOM_C, SOM_L, SOM_M, SOM_KD, SOM_MP, SOM_SvD)

It throws the following error.

> output <- lapply(plist, response, p = "f76a")

Error in `vec_slice()`:
! Can't use character names to index an unnamed vector.
Run `rlang::last_error()` to see where the error occurred.
lapply dataframe r list
1 Answers

You should not collect several data frames using c(). You should use list(). So the following fix should work:

plist <- list(SOM_V, SOM_SD, SOM_C, SOM_L, SOM_M, SOM_KD, SOM_MP, SOM_SvD)

output <- lapply(plist, response, p = "f76a")

Compare the differences:

dat <- data.frame(a = 1:2, b = c("x", "y"))

## becomes a list of vectors
c(dat, dat)
#$a
#[1] 1 2
#
#$b
#[1] "x" "y"
#
#$a
#[1] 1 2
#
#$b
#[1] "x" "y"

## correct: a list of two data frames
list(dat, dat)
user_48917380
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