matching and counting strings (k-mer of DNA) in R

Question

I have a list of strings (DNA sequence) including A,T,C,G. I want to find all matches and insert into table whose columns are all possible combination of those DNA alphabet (4^k

Answer 1

May be this helps

 source("http://bioconductor.org/biocLite.R")
 biocLite("Biostrings")
 library(Biostrings)
 t(sapply(DNAlst, function(x){x1 <-  DNAString(x)
                   oligonucleotideFrequency(x1,2)}))
  #     AA AC AG AT CA CC CG CT GA GC GG GT TA TC TG TT
  #[1,]  2  1  0  1  1  0  0  1  1  0  0  0  0  0  1  3
  #[2,]  5  1  1  2  0  1  1  0  2  0  0  1  2  0  1  0
  #[3,]  0  0  0  2  0  0  0  0  0  1  0  0  1  0  1  1
  #[4,]  0  0  0  0  0  0  0  0  1  0  1  0  0  0  1  0
  #[5,]  1  0  0  1  2  0  2  0  0  2  0  0  0  1  0  0

Or as suggested by @Arun, convert the list to vector first

   oligonucleotideFrequency(DNAStringSet(unlist(DNAlst)), 2L)
   #     AA AC AG AT CA CC CG CT GA GC GG GT TA TC TG TT
   #[1,]  2  1  0  1  1  0  0  1  1  0  0  0  0  0  1  3
   #[2,]  5  1  1  2  0  1  1  0  2  0  0  1  2  0  1  0
   #[3,]  0  0  0  2  0  0  0  0  0  1  0  0  1  0  1  1
   #[4,]  0  0  0  0  0  0  0  0  1  0  1  0  0  0  1  0
   #[5,]  1  0  0  1  2  0  2  0  0  2  0  0  0  1  0  0