On Aug 2, 2012, at 2:27 PM, rnewbie565 wrote:
I am trying to count the number of times that the characters in a
string
change
For example-
new=c(AAAABBBBBABBBABB)
Presumably you meant to quote that string.
I want to find the number of times that B changes to A and the
number of
times that A changes to B. I tried the grep command but I only
figured out
the positions of when B changes to A when I only need the number of
times it
occurs.
> new=c('AAAABBBBBABBBABB')
> unlist(strsplit(new,""))
[1] "A" "A" "A" "A" "B" "B" "B" "B" "B" "A" "B" "B" "B" "A" "B" "B"
> rle(unlist(strsplit(new,"")))
Run Length Encoding
lengths: int [1:6] 4 5 1 3 1 2
values : chr [1:6] "A" "B" "A" "B" "A" "B"
> paste0( rle(unlist(strsplit(new,"")))$values, collapse="")
[1] "ABABAB"
> gregexpr("AB", .Last.value)
[[1]]
[1] 1 3 5
attr(,"match.length")
[1] 2 2 2
attr(,"useBytes")
[1] TRUE
So the length of that list value could be used for the AB transitions.
Similarly for the BA ones
> strrle <- paste0( rle(unlist(strsplit(new,"")))$values, collapse="")
> length( gregexpr("BA", strrle)[[1]] )
[1] 2
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