Preallocating a dataframe in R with date as the column class

Question

I want to preallocate space for dates in an R dataframe.

To preallocate space for characters and numbers, I would write

MyDataframe <- data.frame(Name = character(10), 
                          Tickets  = numeric(10))

What would I add next to preallocate space for dates? This does not work...

# DOES NOT WORK
MyDataframe <- data.frame(Name = character(10), 
                          Tickets  = numeric(10)
                          Date = Date(10))

Currently, I define the column as numeric, then coerce to dates, but this seems less than ideal.
Thanks

Your second code snippet does not work because you are missing a comma. Even then it would still not work because you are calling a function that does not exist, `Date()`. Finally if you mention something not working, its always helpful to give the error message you actually see. See [here](http://stackoverflow.com/questions/5963269/how-to-make-a-great-r-reproducible-example) for tips on how to make a reproducible R question. — Andy, Aug 10 '12 at 16:24
Just had the same question - and went round the same loops trying to find a fun that would pre-allocate for dates. Useful solution. I am in general not in favour of filling cells with fake data though. However it looks like there is no way around it in this case. — Heather Stark, Feb 01 '13 at 10:09

score 5 · Accepted Answer · answered Aug 10 '12 at 16:18

If all you are looking for is a placeholder column with 10 dates, this works:

as.Date(1:10, origin=Sys.Date())

Your problem is that the character() and numeric() functions take a length argument, but as.Date (as there is no Date() function) does not (?as.Date)

score 1 · Answer 2 · answered Aug 12 '12 at 17:37

Here is my final code. It works well.

MyDF <- data.frame(Name = character(10),
                   Tickets = numeric(10),
                   Date = as.Date(rep(0,10), origin = "1900-01-01"))

Here is the output:

> MyDF

   Name Tickets       Date
1             0 1900-01-01
2             0 1900-01-01
3             0 1900-01-01
4             0 1900-01-01
5             0 1900-01-01
6             0 1900-01-01
7             0 1900-01-01
8             0 1900-01-01
9             0 1900-01-01
10            0 1900-01-01

And the summary

> summary(MyDF)

 Name     Tickets       Date           
 :10   Min.   :0   Min.   :1900-01-01  
       1st Qu.:0   1st Qu.:1900-01-01  
       Median :0   Median :1900-01-01  
       Mean   :0   Mean   :1900-01-01  
       3rd Qu.:0   3rd Qu.:1900-01-01  
       Max.   :0   Max.   :1900-01-01

Thanks for your help

I would add the argument `stringsAsFactors=FALSE` to `data.frame()`. Otherwise if your `default.stringsAsFactors=TRUE` then character variables will be coerced to Factors with one level and attempts to add values will yield NAs. — MattBagg, May 19 '14 at 21:06

Preallocating a dataframe in R with date as the column class

2 Answers2