[R-sig-eco] a question of Data quotation

[Christian Parker]

Zongshan,

When you use cbind, R will combine them as a matrix and unfortunately 
the $ way of indexing columns does not work for matrices. A better way 
to get what you want would be like this:

data<-data.frame(jan=npp$JAN,feb=npp$FEB)
      

Hope this helps,
Chris


Zongshan, Li wrote:
> Dear the friends of R-Ecology:
>      I am a beginner for R language, therefore I am sure that this question is possibly quite simple, but it still mean a big problem to me.
>       I select two columns of 'npp' to combine a new variable:data, and give its colnames as jan and feb, the code is following:
>
>       data<-cbind(npp$JAN,npp$FEB)
>       colnames(data)<-c("jan","feb")
>
>       I found that the columns of 'data',could not quoted as 'data$jan',or'data$feb',but can quoted well as data[,1] or data[,2].
>
>       Tips of R-software is 'data$jan : $ operator is invalid for atomic vectors'
>
>       I try to use the function 'as.matrix' convert the data to numeric type,but get the just same result. I am confused about this problem.  
>
> Any help is strongly appreciated,
> thank you in advance,
>
>
> Zongshan, Li£¬zsli_st at rcees.ac.cn
> 2009-12-01 
> Research Center for Eco-Environmental Sciences,Chinese Academy of Sciences
> Shuangqing Road, Haidian street, Beijing, 100085
> Tel: 86-10-13699145748
> QQ: 1141958023
> email: zsli_st at rcees.ac.cn
> website: http://www.rcees.ac.cn/  
>
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>
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