R help - Mar 2003 - overlapping pattern match

Hi, all,
     I have a string like  "aaacdf",  I want to find how many
"aa" in the
string. Obviously, It is 2 in this case.  it is easy to do in Perl, but how
to do such  overlapping match in R or Splus.  Thanks!

Y.Fan

Here''s a way.

string <- "aaacdf"
pattern <- "aa"
nstring <- nchar(string)
npattern <- nchar(pattern)
stringlist <- substring(string, 1:(nstring-npattern+1), npattern:nstring)
sum(stringlist==pattern)

Also, have a look at: pmatch, charmatch, grep, sub, gsub, regexpr, chartr. I 
couldn''t find a simple function to do what you want.

Hope this helps.

Jerome

On March 27, 2003 05:34 pm, Yiping Fan wrote:
> Content-Length: 360
> Status: R
> X-Status: N
>
> Hi, all,
>      I have a string like  "aaacdf",  I want to find how many
"aa" in the
> string. Obviously, It is 2 in this case.  it is easy to do in Perl, but how
> to do such  overlapping match in R or Splus.  Thanks!
>
> Y.Fan
>
> ______________________________________________
> R-help at stat.math.ethz.ch mailing list
> https://www.stat.math.ethz.ch/mailman/listinfo/r-help

try with this:

your.string <- "aaacdf"
nc1 <- nchar(your.string)-1
x <- unlist(strsplit(cadena, NULL)) 
x2 <- c()
for (i in 1:nc1)
  x2 <- c(x2, paste(x2[i], x2[i+1], sep=""))
cat("ocurrences of <aa> in <your.string>:",
length(grep("aa", x2)),
  sep="", fill=TRUE)

Hope it helps!
Fran

--- original message ---
Hi, all,
     I have a string like  "aaacdf",  I want to find how many
"aa" in
the string. Obviously, It is 2 in this case.  it is easy to do in Perl, 
but how to do such  overlapping match in R or Splus.  Thanks!

Y.Fan