[R] levels() function for a vector

[Richard Pearson]

Karen

levels returns the levels attribute of a variable, and a vector has no 
such attribute. This is usually used with a factor, e.g.

 > temp <- c(3, 5, 5, NA)
 > levels(factor(temp))
[1] "3" "5"

Best wishes

Richard


Chang Liu wrote:
> Hello:
>  
> I'm trying to use levels function, but I don't know why it's returning NULL. For example:
>  
>   
>> temp[1]  3  5  5 NA> levels(temp)NULL>
>>     
>  
> Also, I've tried: 
>   
>> list(temp)[[1]][1] "3" "5" "5" NA 
>> levels(list(temp))NULL
>>     
> Is there a specific requirement on the parameter?
>  
> Karen
>  
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