R help - Apr 2010 - selecting rows based on number that occurs after letter

Hello,

I am trying to cycle through a csv and make some summary statistics.
I need to select rows based on the number in the row name that comes
after the letter 'y'. For example, ? BA1y1 would equal 1, ?C3A2r3y1
would equal 1 and ?MA3r3y1r3 would equal 1.

I currently have my code ?cycling through by the 5th character but my
rows have variable length and the y can occur in several different
locations in the row name.

Here is my current code

sdat <- read.csv (paste(data.dir,"/summary.data.csv",
sep=""))

year <-c("1", "2", "3")
for (y in year) {

sdat2 <- sdat[sapply(strsplit(as.character(sdat$GCM), ""),
function(zzz)zzz[5] == y),]

Thanks
Daisy Englert Duursma

Bioclimatic Modeller
Macquarie University
Sydney, NSW, Australia

Use regular expressions:
> x <- c( "BA1y1", "C3A2r3y1", "MA3r3y1r3",
"MA23r34y123z99")
> # extact the number after the 'y'
> num <- sub(".*y(\\d <file://d/>+).*", "\\1
<file://0.0.0.1/>", x)
>
> num
[1] "1"   "1"   "1"  
"123"
>

On Sun, Apr 18, 2010 at 8:41 PM, Daisy Englert Duursma <
daisy.duursma@gmail.com> wrote:
> Hello,
>
> I am trying to cycle through a csv and make some summary statistics.
> I need to select rows based on the number in the row name that comes
> after the letter 'y'. For example,   BA1y1 would equal 1,  C3A2r3y1
> would equal 1 and  MA3r3y1r3 would equal 1.
>
> I currently have my code  cycling through by the 5th character but my
> rows have variable length and the y can occur in several different
> locations in the row name.
>
> Here is my current code
>
> sdat <- read.csv (paste(data.dir,"/summary.data.csv",
sep=""))
>
> year <-c("1", "2", "3")
> for (y in year) {
>
> sdat2 <- sdat[sapply(strsplit(as.character(sdat$GCM), ""),
> function(zzz)zzz[5] == y),]
>
> Thanks
> Daisy Englert Duursma
>
> Bioclimatic Modeller
> Macquarie University
> Sydney, NSW, Australia
>
> ______________________________________________
> 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<http://www.r-project.org/posting-guide.html>
> and provide commented, minimal, self-contained, reproducible code.
>


-- 
Jim Holtman
Cincinnati, OH
+1 513 646 9390

What is the problem that you are trying to solve?

	[[alternative HTML version deleted]]

Hello,

Thanks for your help, I have played around with the suggestion a bit
but I can still not sub-setting in the way I need

If I have a matrix x as follows:

  > x <-
matrix(c("BA1y1","BA2y3","C3A1r1y1","C3A2r2y2t4","C3r2y1y1",1,2,3,
11,12)
, nrow=5, ncol=2,
dimnames=list(c("a","b","c","d","e"),
c("GCM","y")))
  > x
  GCM          y
a "BA1y1"      "1"
b "BA2y3"      "2"
c "C3A1r1y1"   "3"
d "C3A2r2y2t4" "11"
e "C3r2t1y1"   "12"

and I want to loop through 3 subsets based on the numeric value after
the y, how do I do this?

What I currently have is:
> year <-c("1", "2", "3")
> for (y in year) {
> subx <- x[sapply(strsplit(as.character(x$GCM), ""),
function(zzz)zzz[5] == y),]
}
Basically this loops through and subsets the rows when the 5th
character has the defined y value (1, 2,or 3). The problem is that y
can occur anywhere in the GCM value.

Thanks for the help.
Daisy
--
Daisy Englert Duursma

Room E8C156
Dept. Biological Sciences
Macquarie University  NSW  2109
Australia

Tel +61 2 9850 9256