Re: [R] how to get the numbers of factors in a matrix

[张以春]

Dear Jun Yi,


Thank you very much for your help. But, the link you attached can not resolve 
my question.


What I want is to get the numbers of factor levels for every subsets of a 
vector. When I do this, it always gives me the total numbers of levels for the 
whole vector. It really makes me confused. 


Best,
Yichun



> -----原始邮件-----
> 发件人: "Liu, Jun Yi" <7yu...@gmail.com>
> 发送时间: 2014年1月21日 星期二
> 收件人: "张以春" <yczh...@nigpas.ac.cn>, r-help@r-project.org
> 抄送: 
> 主题: Re: [R] how to get the numbers of factors in a matrix
> 
> 
> Dear YZ,
> 
> I guess this is what you want:
> 
> 1. 
> http://stackoverflow.com/questions/3418128/how-to-convert-a-factor-to-an-integer-numeric-without-a-loss-of-information
> 2. 
> http://stackoverflow.com/questions/6979625/arithmetic-operations-on-r-factors/6980780#6980780
> 3. 
> http://toddjobe.blogspot.jp/2010/08/converting-r-contingency-tables-to-data.html
> 
> but beware of that “If you really want the levels of the factor to be used, 
> you're either doing something very wrong or too clever for its own good."
> 
> All the best 
> JY
> 
> ------------------------------------------------------
> From: 张以春 yczh...@nigpas.ac.cn
> Reply: 张以春 yczh...@nigpas.ac.cn
> Date: 21 January 2014 at 16:57:38
> To: r-help@r-project.org r-help@r-project.org
> Subject:  [R] how to get the numbers of factors in a matrix
> 
> >  
> > Dear friends,
> >  
> >  
> > I have a question do not know how to resolve.
> >  
> >  
> > I have a big matrix composed of different columns (I use N here).  
> > A column is "species" and another one is "latitudes". Now, I want  
> > to know how I can get the number of different "latitudes" for every  
> > "species". I have tried to split the matrix according to species  
> > (X<-split(N, N$species) and then use sapply(X, 
> > function(m){nlevels(m$latitudes)})  
> > to get that. But the result shows the total factor numbers of "latitudes"  
> > but not the factor numbers of every species I splitted. Also,  
> > I have tried to use tapply(N$latitudes, N$species, nlevels)  
> > to do this. The result is the same. I am confused about this. Can  
> > someone help me with that? Thank you very much!
> >  
> >  
> > Best regards,
> > Yichun
> >  
> >  
> >  
> >  
> >  
> >  
> > [[alternative HTML version deleted]]
> >  
> > ______________________________________________
> > R-help@r-project.org mailing list
> > https://stat.ethz.ch/mailman/listinfo/r-help
> > PLEASE do read the posting guide 
> > http://www.R-project.org/posting-guide.html  
> > and provide commented, minimal, self-contained, reproducible  
> > code.
> >  
> 



--
Dr Yichun Zhang
State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of 
Geology and Palaeontology
39 East Beijing Road, Nanjing, China, 210008




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