R help - Sep 2008 - Finding a vector position using names rather than values

Dear R gurus,

I have been struggling with this for a while and thought you might be able to
give me some guidance.

I have a data frame, on which I apply a row function.  The result looks to me
like a vector that retains the old row names.  I then sort the vector and
subsequently need to be able to identify the rank of certain values by searching
for their row names.  See this mock example:
> dframe <- data.frame("Col1"=c(10,20,30),
"Col2"=c(2,4,6), "Col3"=c(5,10,7),
row.names=c("R1","R2","R3"))
> row_median<-apply(dframe,1,median)
> row_median.sorted <- sort(row_median, decreasing=TRUE)
> row_median.sorted
R2 R3 R1 
10  7  5 

I now want to know the rank of, say R3 in this vector.  I know I can use match()
to find this using the vector values, however I need to use the header names
(eg. "R3") rather than the value (7).

Many thanks for your help,
Pall

try this:

dframe <- data.frame(
	Col1 = c(10,20,30),
	Col2 = c(2,4,6),
	Col3 = c(5,10,7),
	row.names = c("R1","R2","R3")
)

mat <- data.matrix(dframe)
rowMedians <- apply(mat, 1, median)
rowMedians[names(rowMedians) %in% "R3"]


I hope it helps.

Best,
Dimitris

> Dear R gurus,
>
> I have been struggling with this for a while and thought you might be able
> to give me some guidance.
>
> I have a data frame, on which I apply a row function.  The result looks to
> me like a vector that retains the old row names.  I then sort the vector
> and subsequently need to be able to identify the rank of certain values by
> searching for their row names.  See this mock example:
>
>> dframe <- data.frame("Col1"=c(10,20,30),
"Col2"=c(2,4,6),
>> "Col3"=c(5,10,7),
row.names=c("R1","R2","R3"))
>> row_median<-apply(dframe,1,median)
>> row_median.sorted <- sort(row_median, decreasing=TRUE)
>
>> row_median.sorted
> R2 R3 R1
> 10  7  5
>
> I now want to know the rank of, say R3 in this vector.  I know I can use
> match() to find this using the vector values, however I need to use the
> header names (eg. "R3") rather than the value (7).
>
> Many thanks for your help,
> Pall
>
> ______________________________________________
> 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.
>

-- 
Dimitris Rizopoulos
Assistant Professor
Department of Biostatistics
Erasmus University Medical Center

Address: PO Box 2040, 3000 CA Rotterdam, the Netherlands
Tel: +31/(0)10/7043478
Fax: +31/(0)10/7043014

Try this:

order(row_median)[names(row_median) == "R3"]

On Fri, Sep 12, 2008 at 5:22 AM, Jonsson, Pall
<Pall.Jonsson@astrazeneca.com
> wrote:
> Dear R gurus,
>
> I have been struggling with this for a while and thought you might be able
> to give me some guidance.
>
> I have a data frame, on which I apply a row function.  The result looks to
> me like a vector that retains the old row names.  I then sort the vector
and
> subsequently need to be able to identify the rank of certain values by
> searching for their row names.  See this mock example:
>
> > dframe <- data.frame("Col1"=c(10,20,30),
"Col2"=c(2,4,6),
> "Col3"=c(5,10,7),
row.names=c("R1","R2","R3"))
> > row_median<-apply(dframe,1,median)
> > row_median.sorted <- sort(row_median, decreasing=TRUE)
>
> > row_median.sorted
> R2 R3 R1
> 10  7  5
>
> I now want to know the rank of, say R3 in this vector.  I know I can use
> match() to find this using the vector values, however I need to use the
> header names (eg. "R3") rather than the value (7).
>
> Many thanks for your help,
> Pall
>
> ______________________________________________
> 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.
>


-- 
Henrique Dallazuanna
Curitiba-Paraná-Brasil
25° 25' 40" S 49° 16' 22" O

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