Create a Data frame with one line and Null Values on R-CodePudding

I would like to create a dataframe with a single line with NULL values for the columns "Date", "p.value" and "User", but I'm not suceeding with the code below:

df <- data.frame(Date=NULL, "p.value"=NULL, User=NULL)

Does anyone know how to solve it?

CodePudding user response：

For an empty dataframe, you can initialize a vector with the class (e.g., character). If you are needing a date format, then you can wrap as.Date around character.

df <- data.frame(Date=as.Date(character()),
                 "p.value"=character(), 
                 User=character(), 
                 stringsAsFactors=FALSE)

#[1] Date    p.value User   
#<0 rows> (or 0-length row.names)

Or you could use NA if you need an actual row. But this defaults to logical for class. So, if you need columns to be a particular class, then you would still need to wrap the class around the NA (e.g., as.character(NA)).

df <- data.frame(Date=NA, "p.value"=NA, User=NA, 
                 stringsAsFactors=FALSE)

#  Date p.value User
#1   NA      NA   NA

You can use NULL as character, but I don't think it's possible to have only a NULL row.

CodePudding user response：

This seems to work too:

example_df <- data.frame( "date" = character(0), "p.value" = integer(0), "USER" = integer(0))

Comes up with this:

[1] date p.value USER
<0 rows> (or 0-length row.names)