[R] Help on efficiency/vectorization

[Moshe Olshansky]

You can do

for (i in 1:ncol(x)) {names <- rownames(x)[which(x[,i]==1)];eval(parse(text=paste("V",i,".ind<-names",sep="")));}



--- On Thu, 27/8/09, Steven Kang <stochastickang at gmail.com> wrote:

> From: Steven Kang <stochastickang at gmail.com>
> Subject: [R] Help on efficiency/vectorization
> To: r-help at r-project.org
> Received: Thursday, 27 August, 2009, 4:13 PM
> Dear R users,
> 
> I am trying to extract the rownames of a data set for which
> each columns
> meet a certain criteria. (condition - elements of each
> column to be equal
> 1)
> 
> I have the correct result, however I am seeking for more
> efficient (desire
> vectorization) way in implementing such problem as it can
> get quite messy if
> there are hundreds of columns.
> 
> Arbitrary data set and codes are shown below for your
> reference:
> 
> x <- as.data.frame(matrix(round(runif(50),0),nrow=5))
> 
> rownames(x) <- letters[1:dim(x)[1]]
> 
> > x
>   V1 V2 V3 V4 V5 V6 V7 V8 V9 V10
> a  0  1   1   
> 1   0   0   
> 0   0   1    0
> b  1  1   1   
> 1   0   1   
> 0   0   1    1
> c  0  1   1   
> 0   0   0   
> 0   0   0    1
> d  1  0   0   
> 1   1   1   
> 1   1   0    0
> e  1  0   0   
> 0   0   1   
> 1   0   1    0
> 
> V1.ind <- rownames(x)[x[,"V1"]==1]
> V2.ind <- rownames(x)[x[,"V2"]==1]
> V3.ind <- rownames(x)[x[,"V3"]==1]
> V4.ind <- rownames(x)[x[,"V4"]==1]
> :
> :
> V10.ind <- rownames(x)[x[,"V10"]==1]
> 
> > V1.ind
> [1] "b" "d" "e"
> > V2.ind
> [1] "a" "b" "c"
> > V3.ind
> [1] "a" "b" "c"
> :
> :
> > V10.ind
> [1] "b" "c"
> 
> 
> 
> Your expertise in resolving this issue would be highly
> appreciated.
> 
> 
> Steve
> 
>     [[alternative HTML version deleted]]
> 
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