[R] Using regular expressions to detect clusters of consonants in a string

[Greg Hirson]

Mark,

"Abstraction" also has a valid two consonant cluster ("ct"). Some logic 
could be added to reject words that have valid twos if they also have 
longer strings of consonants.

This may work as a starting off point, using strsplit:

twocons = function(word){
    chars = strsplit(word, "[aeiou]")
    conlengths = lapply(chars, nchar)
    numtwos = sum(conlengths[[1]] == 2)
    return(numtwos)
    }

words = c("test", "hello", "fail", "pass", "assess")

lapply(words, twocons)
[[1]]
[1] 1

[[2]]
[1] 1

[[3]]
[1] 0

[[4]]
[1] 1

[[5]]
[1] 2



I hope this is helpful,

Greg

Mark Heckmann wrote:
> Hi,
>
> I want to parse a string extracting the number of occurrences where two
> consonants clump together. Consider for example the word "hallo". Here I
> want the algorithm to return 1. For "chess" if want it to return 2. For the
> word "screw" the result should be negative as it is a clump of three
> consonants not two. Also for word "abstraction" I do not want the algorithm
> to detect two times a two consonant cluster. In this case the result should
> be negative as well as it is four consonants in a row.
>
> str <- "hallo"
> gregexpr("[bcdfghjklmnpqrstvwxyz]{2}[aeiou]{1}" , str, ignore.case =TRUE,
> extended = TRUE)[[1]]
>
> [1] 3
> attr(,"match.length")
> [1] 3
>
> The result is correct. Now I change the word to "hall"
>
> str <- "hall"
> gregexpr("[bcdfghjklmnpqrstvwxyz]{2}[aeiou]{1}" , str, ignore.case =TRUE,
> extended = TRUE)[[1]]
>
> [1] -1
> attr(,"match.length")
> [1] -1
>
> Here my expression fails. How can I write a correct regex to do this? I
> always encounter problems at the beginning or end of a string.
>
> Also:
>
> str <- "abstraction"
> gregexpr("[bcdfghjklmnpqrstvwxyz]{2}[aeiou]{1}" , str, ignore.case =TRUE,
> extended = TRUE)[[1]]
>
> [1] 4 7
> attr(,"match.length")
> [1] 3 3
>
> This also fails.
>
> Thanks in advance,
> Mark
>
> -------------------------------
> Mark Heckmann
> www.markheckmann.de
> R-Blog: http://ryouready.wordpress.com
>
> ______________________________________________
> 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.
>   

-- 
Greg Hirson
ghirson at ucdavis.edu

Graduate Student
Agricultural and Environmental Chemistry

1106 Robert Mondavi Institute North
One Shields Avenue
Davis, CA 95616