[Rd] corrupt data frame: columns will be truncated or padded with NAs in: format.data.frame(x, digits = digits)

Prof Brian Ripley ripley at stats.ox.ac.uk
Mon Feb 14 12:38:22 CET 2005

On Mon, 14 Feb 2005, Gregor GORJANC wrote:

> Prof Brian Ripley wrote:

>> You did create a corrupt data frame by using *replacement* on part of 
>> something that did not exist.  The simple workaround is not to do that. One 
>> can argue about what should happen in such a case and currently R assumes 
>> that you know what you are doing and will only treat the data frame as a 
>> list. We could make this an error, but that would add an overhead to be 
>> paid by careful users too.

> I agree to some extent, however I was very surprised of this behaviour. I 
> often deal with data that have missing values and now I really do not know 
> how to manage such data. How can one add a column to existing data frame
> in such a way, that you don't get corrupted data frames as in my example?

You add a column, not replace part of a non-existent column.  Isn't that 
obvious, given what you wrote?

There is a lot of basic documentation on data manipulation in R/S, and a 
whole chapter in MASS4.  Somehow most other people don't seem to find this 
a problem.

Brian D. Ripley,                  ripley at stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272866 (PA)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595

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