please excuse me if my question is quite basic.
I created an empty data frame by df <- data.frame()
and obviously the data frame is NULL (empty). when I try to check if the data frame is empty by is.null(df)
, the result comes FALSE. Is there any difference between NULL
and empty
in R. In this case if the data frame is not NULL
, then what is in the empty data frame and when it will be NULL
. Thanks
df
is not NULL because it is a data frame and thus has some defined properties. For instance, it has a class. And you can get the number of rows in the data frame using nrow(df)
, even if the result should happen to be zero. Therefore, also the number of rows is well-defined.
As fas as I know, there is no is.empty
command in base R. What you could do is, e.g., the following
is.data.frame(df) && nrow(df)==0
This will give TRUE for an empty data frame (that is, one with no rows) and false otherwise.
The reason for checking is.data.frame
first is that nrow
might cause an error, if it is applied to anything else than a data frame. Thanks to &&
, nrow(df)
will only be evaluated if df
is a data frame.