[R] Division of data frame and deletion of values from column

[David Winsemius]

On Oct 16, 2009, at 12:16 PM, Joel Fürstenberg-Hägg wrote:

>
> Hi all,
>
> I guess this might be an easy question, but I've searched multiple  
> help pages without finding any answear... so now I put my trust in  
> you!
>
> I have a data frame (36 variables and 556 observations). One column  
> contains  three factors, and I would like to divide the data frame  
> into three new ones, based on the value of the factors, thereby  
> having only one value for all elements of the particular column in  
> each of the data frames. The reason is that I later will create  
> plots and do statistical analyzes on these data frames, and I don't  
> want those factors affecting the result.
>    ID Weight  Age_days ...
> 1   18   76.1       106
> 2   19   77.0       175
> 3   20   78.1       121
> 4   21   78.2       121
> 5   22   78.8       106
> 6   23   76.3       106
> .
> .
> .

?split


>
> I also have another column containing several factors, of which I  
> would like to exclude one (get NA instead).
>
>    ID Weight  Age_days  Value_ID ...
> 1   18   76.1       106      high
> 2   19   77.0       175       low
> 3   20   78.1       121    middle
> 4   21   78.2       121      high
> 5   22   78.8       106      high
> 6   23   76.3       106    number   <-- exclude
> 7   24   76.9       175       low
> .
> .
> .

?is.na    # which has an is.na(<- capacity

>
> I really hope someone could help me, though you might think it's too  
> easy...
>
> Best regards,
>
> Joel
> 		 	   		

David Winsemius, MD
Heritage Laboratories
West Hartford, CT