R help - Jul 2002 - How to get relevant dimnames from apply() ?

Hello,

in order to vectorize task (of plotting barplots), I use, as probably all
R-folks, function apply()
instead of for() loop.

<R>
testarr<-matrix(1:30, nrow=5)
rownames(testarr)<-letters[1:5]
colnames(testarr)<-LETTERS[1:6]
apply(testarr,1,function(x) {x11(); barplot(x)}) #the funcion used is
actually more compex, but it doesn't matter
</R>

Now, how I can propagate the rownames of testarr into the main label of
plot via

main="what_should_I_paste_here?"

Asking for
<R>
str(apply(testarr,1,function(x) {x11(); barplot(x)}))
</R>
gives

<Routput>
 num [1:6, 1:5] 0.7 1.9 3.1 4.3 5.5 ...
 - attr(*, "dimnames")=List of 2
  ..$ : NULL
  ..$ : chr [1:5] "a" "b" "c" "d" ...
</Routput>

but how it is possible to put dimnames of _this_ (i.e., the rownames of
testarr) into "main" label of a plot?
With for() loop, the task is trivial, but with apply?
The problem I need to solve is OK (in terms of performance) with for()
loops, but apply is more elegant
and , of course, much more in R-style...

Thanks,
Jan

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/- Jan Svatos,  PhD         Sokolovska 855/225 -/
/- Data Analyst             Prague 9           -/
/- Eurotel Praha            190 00             -/
/- jan_svatos at eurotel.cz    Czechia            -/
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Jan_Svatos at eurotel.cz wrote:
Hi,
why not binding the names to the matrix? 
> 
> Hello,
> 
> in order to vectorize task (of plotting barplots), I use, as probably all
> R-folks, function apply()
> instead of for() loop.
> 
> <R>
> testarr<-matrix(1:30, nrow=5)
> rownames(testarr)<-letters[1:5]
> colnames(testarr)<-LETTERS[1:6]
> apply(testarr,1,function(x) {x11(); barplot(x)}) #the funcion used is
> actually more compex, but it doesn't matter
> </R>
This would ad something like the following to your code:

hurz <- cbind(testarr, names=rownames(testarr))
hurz
apply(hurz, 1, function(x) { 
		x11(); 
		barplot(as.numeric(x[names(x)!='nams']), 
		  names.arg = names(x[names(x)!='nams']), 
		  main=x['nams'])
		} ) 

You might decide for yourself if this is more elegant than a for loop.

Michael
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