What is an easy way to find out what class each column is in a data frame is?
This question is related to
r
One option is to use lapply and class. For example:
> foo <- data.frame(c("a", "b"), c(1, 2))
> names(foo) <- c("SomeFactor", "SomeNumeric")
> lapply(foo, class)
$SomeFactor
[1] "factor"
$SomeNumeric
[1] "numeric"
Another option is str:
> str(foo)
'data.frame': 2 obs. of 2 variables:
$ SomeFactor : Factor w/ 2 levels "a","b": 1 2
$ SomeNumeric: num 1 2
You can simple make use of lapply or sapply builtin functions.
lapply will return you a list -
lapply(dataframe,class)
while sapply will take the best possible return type ex. Vector etc -
sapply(dataframe,class)
Both the commands will return you all the column names with their respective class.
Hello was looking for the same, and it could be also
unlist(lapply(mtcars,class))
I wanted a more compact output than the great answers above using lapply, so here's an alternative wrapped as a small function.
# Example data
df <-
data.frame(
w = seq.int(10),
x = LETTERS[seq.int(10)],
y = factor(letters[seq.int(10)]),
z = seq(
as.POSIXct('2020-01-01'),
as.POSIXct('2020-10-01'),
length.out = 10
)
)
# Function returning compact column classes
col_classes <- function(df) {
t(as.data.frame(lapply(df, function(x) paste(class(x), collapse = ','))))
}
# Return example data's column classes
col_classes(df)
[,1]
w "integer"
x "character"
y "factor"
z "POSIXct,POSIXt"
You can use purrr as well, which is similar to apply family functions:
as.data.frame(purrr::map_chr(mtcars, class))
purrr::map_df(mtcars, class)
Source: Stackoverflow.com