Getting the class of all columns of data.frames in a list

Question

Example Data:

df1 <- as.data.frame(rbind(c(1,2,3), c(1, NA, 4), c(NA, NA, NA), c(4,6,7), c(4, 8, NA)))
df2 <- as.data.frame(rbind(c(1,2,3), c(1, NA, 4), c(4,6,7), c(NA, NA, NA), c(4, 8, NA)))

dfList <- list(df1,df2)
colnames <- c("A","B","C") 

dfList[[1]]

  V1 V2 V3
1  1  2  3
2  1 NA  4
3 NA NA NA
4  4  6  7
5  4  8 NA

dfList[[2]]

  V1 V2 V3
1  1  2  3
2  1 NA  4
3  4  6  7
4 NA NA NA
5  4  8 NA

I would like to do some checks on my list of data.frames. For example, see if all the columns in the first data.frame have the same classes as the columns in the other data.frames. I thought I'd try:

dfList <- lapply(dfList , function(x) lapply(class(x)))

But that does not work. What would be the correct syntax for this?

replace `lapply(class(x))` with `lapply(x, class)` – det Dec 04 '20 at 11:22 — det, Dec 04 '20 at 11:22
Note that `sapply` will output a vector of classes. – SteveM Dec 04 '20 at 11:35 — SteveM, Dec 04 '20 at 11:35

score 0 · Accepted Answer · answered Jan 05 '21 at 13:03

0

Credit to @det (see comments).

dfList <- lapply(dfList , function(x) lapply(x, class))

answered Jan 05 '21 at 13:03

Tom

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Getting the class of all columns of data.frames in a list

1 Answers1