[R] Need Help for creating a new variable

[Mark Difford]

Hi Chun,

>> I did do the research and work on for hours ... I try to creat a new
>> variable in my dataset.

Yes, looks like you did. Look at ?interaction, which gives you more
flexibility than ?":".

## Example
diet<-sort(rep(x=c("C","T"),4)) 
vesl<-rep(x=c("A","P"),4) 
mydata<-data.frame(diet,vesl)

mydata$trt <- interaction(mydata$diet, mydata$vesl)
mydata

mydata$trt <- mydata$diet:mydata$vesl
mydata

Regards, Mark.


Chun-Hao Tu wrote:
> 
> 
> 
> Hi R users,
> 
> I did do the research and work on for hours, but I still don't know how to
> solve my silly problem. I try to creat a new variable in my dataset.
> 
> such as if diet=="C" && vesl=="P" then trt="CP";  if diet=="C" &&
> vesl=="A" then trt="CA";.....  The following is my code (It does not work
> correctly). 
> 
> Could anyone give me a hint? Appreciate!
> 
>  
> 
>> diet<-sort(rep(x=c("C","T"),4))
>> vesl<-rep(x=c("A","P"),4)
>> mydata<-data.frame(diet,vesl)
>> 
>> mydata$trt<-ifelse(mydata$diet=="C" && mydata$vesl=="A", "CA",
> +            ifelse(mydata$diet=="C" && mydata$vesl=="P", "CP",
> +              ifelse(mydata$diet=="T" && mydata$vesl=="A", "TA",
> +                 ifelse(mydata$diet=="T" && mydata$vesl=="P", "TP"))))
>> mydata
>   diet vesl trt
> 1    C    A  CA
> 2    C    P  CA
> 3    C    A  CA
> 4    C    P  CA
> 5    T    A  CA
> 6    T    P  CA
> 7    T    A  CA
> 8    T    P  CA
> 
>  
> 
> Thank you very much
> 
>  
> 
> Chunhao
> 
> _________________________________________________________________
> 
> 
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