[R] matrix not working

[David Winsemius]

On May 26, 2011, at 1:53 PM, Andy Zhu wrote:

> Dat:
>
> 1. you can use as.matrix to convert data.frame to matrix;
> 2. it is likely that the internal representation of your data.frame  
> may not be numerical value; matrix can only take on numeric.
>

Not true. Can be any single mode, including "character", "list", and  
"logical".

-- 
david.

>
>
> --- On Thu, 5/26/11, Dat Mai <dat.d.mai at gmail.com> wrote:
>
> From: Dat Mai <dat.d.mai at gmail.com>
> Subject: [R]  matrix not working
> To: r-help at r-project.org
> Date: Thursday, May 26, 2011, 12:24 PM
>
> Hello All,
>
> I'm trying to create a matrix from a dataframe (let's call it df):
> ......a......b.....c.....d
> a   inputs      output
> b   inputs      output
> c   inputs      output
> d   inputs      output
> e   inputs      output
>
> The inputs are represented by columns a and b
> The outputs are represented by columns c and d, but the only outputs  
> are
> those from column d
> - some values from column d are NA
> - column d was created with the code:
>
> df$d=rank(df$c, na.last="keep")
>
> #----------R Code---------#
> item=unique(df$a)
> n=length(list)
>
> r=matrix(data=NA,nrow=n, ncol=n, dimnames=list(PRR1=item, PRR2=item))
>
> for(j in 2:ln)
> {
>   for(i in 1:(j-1))
>   {
>     input1=rownames(r)[i]
>     input2=colnames(r)[j]
>
>     q=df[(df$a==input1 & df$b==input2), "d"]
>
>     if(length(q)==0)
>     {
>       q=df[(df$a==input2 & df$b==input1), "d"]
>     }
>
>     if(length(q)==0)
>     {
>       q=NA
>     }
>
>     r[j,i]=q
>     r[i,j]=q
>     r[j,j]=q
>   }
> }
>
> The result is a matrix with the appropriate dimensions, but  
> everything is
> filled with NA instead of the rankings of the various combinations.  
> I'd like
> for the matrix to be filled with the ranking values--what have I  
> done wrong?
> -- 
> Best,
> Dat Mai
> PhD Rotation Student
> Albert Einstein College of Medicine
>
>     [[alternative HTML version deleted]]
>
> ______________________________________________
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> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>
> 	[[alternative HTML version deleted]]
>
> ______________________________________________
> R-help at 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.

David Winsemius, MD
West Hartford, CT