Tinkering today I wrote a quick toy to generate strings of unique, overlapping kmers. Not particularly efficient, but possibly handy nonetheless.<\/p>\n
It takes a given k size, a configurable overlap and optionally the bases to use. First it generates a list of all the kmers then it recursively scans for matching overlapping kmers and extends a seed, terminating the recursion and printing if all kmers have been used.<\/p>\n
Run it like so:<\/p>\n
.\/kmer-overlap -k=3 -overlap=2 ACTG<\/code><\/pre>\n#!\/usr\/local\/bin\/perl\r\n#########\r\n# Author: rmp\r\n# Created: 2013-05-15\r\n# Last Modified: $Date$\r\n# Id: $Id$\r\n# HeadURL: $HeadURL$\r\n#\r\nuse strict;\r\nuse warnings;\r\nuse Getopt::Long;\r\nuse Readonly;\r\nuse English qw(-no_match_vars);\r\n\r\nReadonly::Scalar our $DEFAULT_K => 3;\r\nReadonly::Scalar our $DEFAULT_BASES => [qw(A C T G)];\r\n\r\nmy $opts = {};\r\nGetOptions($opts, qw(k=s rand help));\r\n\r\nif($opts->{help}) {\r\n print < <\"EOT\"; $PROGRAM_NAME - rmp 2013-05-15 Usage: $PROGRAM_NAME -k=3 -overlap=2 -rand ACTG EOT exit; } my $k = $opts->{k} || $DEFAULT_K;\r\nmy $overlap = $opts->{overlap} || $k-1;\r\nmy $bases = $DEFAULT_BASES;\r\n\r\nif(scalar @ARGV) {\r\n $bases = [grep { $_ } map {split \/\/smx} @ARGV];\r\n}\r\n\r\n#########\r\n# Build all available kmers\r\n#\r\nmy $kmers = [];\r\n\r\nfor my $base1 (@{$bases}) {\r\n build($base1, $bases, $kmers);\r\n}\r\n\r\n#########\r\n# optionally randomise the seeds\r\n#\r\nif($opts->{rand}) {\r\n shuffle($kmers);\r\n}\r\n\r\n#########\r\n# start with a seed\r\n#\r\nfor my $seed (@{$kmers}) {\r\n my $seen = {\r\n\t $seed => 1,\r\n\t };\r\n solve($seed, $seen);\r\n}\r\n\r\nsub build {\r\n my ($seq, $bases, $kmers) = @_;\r\n if(length $seq == $k) {\r\n #########\r\n # reached target k - store & terminate\r\n #\r\n push @{$kmers}, $seq;\r\n return 1;\r\n }\r\n\r\n for my $base (@{$bases}) {\r\n ########\r\n # extend and descend\r\n #\r\n build(\"$seq$base\", $bases, $kmers);\r\n }\r\n\r\n return;\r\n}\r\n\r\nsub solve {\r\n my ($seq_in, $seen) = @_;\r\n\r\n if(scalar keys %{$seen} == scalar @{$kmers}) {\r\n #########\r\n # exhausted all kmers - completed!\r\n #\r\n print $seq_in, \"\\n\";\r\n return 1;\r\n }\r\n\r\n my $seq_tail = substr $seq_in, -$overlap, $overlap;\r\n\r\n my $overlapping = [grep { $_ =~ \/^$seq_tail\/smx } # filter in only seqs which overlap the seed tail\r\n\t\t grep { !$seen->{$_} } # filter out kmers we've seen already\r\n\t\t @{$kmers}];\r\n if(!scalar @{$overlapping}) {\r\n #########\r\n # no available overlapping kmers - terminate!\r\n #\r\n return;\r\n }\r\n\r\n if($opts->{rand}) {\r\n shuffle($overlapping);\r\n }\r\n\r\n my $overhang = $k-$overlap;\r\n for my $overlap_seq (@{$overlapping}) {\r\n #########\r\n # extend and descend\r\n #\r\n my $seq_out = $seq_in . substr $overlap_seq, -$overhang, $overhang;\r\n solve($seq_out, {%{$seen}, $overlap_seq => 1});\r\n }\r\n\r\n return;\r\n}\r\n\r\nsub shuffle {\r\n my ($arr_in) = @_;\r\n for my $i (0..scalar @{$arr_in}-1) {\r\n my $j = int rand $i;\r\n ($arr_in->[$i], $arr_in->[$j]) = ($arr_in->[$j], $arr_in->[$i]);\r\n }\r\n}<\/code><\/pre>\nOutput looks like this:<\/p>\n
epiphyte:~ rmp$ .\/kmer-overlap -k=2 AC\r\nAACCA\r\nACCAA\r\nCAACC\r\nCCAAC<\/code><\/pre>\n","protected":false},"excerpt":{"rendered":"Tinkering today I wrote a quick toy to generate strings of unique, overlapping kmers. Not particularly efficient, but possibly handy nonetheless. It takes a given k size, a configurable overlap and optionally the bases to use. First it generates a list of all the kmers then it recursively scans for matching overlapping kmers and extends … Continue reading “unique, overlapping kmer strings”<\/span><\/a><\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"om_disable_all_campaigns":false,"_monsterinsights_skip_tracking":false,"_uf_show_specific_survey":0,"_uf_disable_surveys":false,"footnotes":""},"categories":[11],"tags":[38,920,21,778],"class_list":["post-735","post","type-post","status-publish","format-standard","hentry","category-programming","tag-bioinformatics","tag-kmers","tag-perl","tag-sequence"],"aioseo_notices":[],"aioseo_head":"\n\t\t\n\t\n\t\n\t\n\t\n\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t