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in reply to Re^2: Fast common substring matching
in thread Fast common substring matching

Okay, but I'm not sure whether you can safetly discount the possibility of long sequences of repeated characters, even in biodata. The following shows a scan of the complete drosophila (fruit fly) genome looking for sequences of repeated DNA characters:

>perl -nlwe" print $1 while m[((.)\2+)]g" na_clones.dros.RELEASE2.5 | +( More? perl -nle"$b{ length($_) }{ chop $_}++ } { printf qq[length %d :[ A:%d C:%d G:%d T:%d ]\n], $_, @{$b{$_}}{'A','C','G','T'} for sort{$b<=>$a} keys %b" ) length 50 :[ A:1 C:0 G:0 T:0 ] length 47 :[ A:1 C:0 G:0 T:0 ] length 45 :[ A:1 C:0 G:0 T:0 ] length 44 :[ A:0 C:0 G:0 T:0 ] length 43 :[ A:0 C:0 G:0 T:1 ] length 42 :[ A:1 C:0 G:0 T:0 ] length 41 :[ A:1 C:0 G:0 T:1 ] length 40 :[ A:1 C:0 G:0 T:0 ] length 39 :[ A:0 C:0 G:0 T:0 ] length 38 :[ A:1 C:0 G:0 T:0 ] length 37 :[ A:2 C:0 G:0 T:0 ] length 36 :[ A:5 C:0 G:0 T:4 ] length 35 :[ A:5 C:0 G:0 T:3 ] length 34 :[ A:2 C:0 G:0 T:3 ] length 33 :[ A:2 C:0 G:0 T:3 ] length 32 :[ A:1 C:0 G:0 T:1 ] length 31 :[ A:5 C:0 G:0 T:5 ] length 30 :[ A:4 C:0 G:0 T:5 ] length 29 :[ A:10 C:0 G:0 T:6 ] length 28 :[ A:12 C:0 G:0 T:13 ] length 27 :[ A:19 C:0 G:0 T:12 ] length 26 :[ A:26 C:0 G:0 T:28 ] length 25 :[ A:35 C:1 G:1 T:34 ] length 24 :[ A:48 C:0 G:0 T:47 ] length 23 :[ A:63 C:0 G:1 T:59 ] length 22 :[ A:78 C:1 G:0 T:84 ] length 21 :[ A:109 C:5 G:3 T:91 ] length 20 :[ A:126 C:5 G:6 T:144 ] length 19 :[ A:188 C:17 G:15 T:148 ] length 18 :[ A:240 C:25 G:26 T:314 ] length 17 :[ A:411 C:45 G:55 T:389 ] length 16 :[ A:647 C:73 G:78 T:656 ] length 15 :[ A:905 C:122 G:133 T:886 ] length 14 :[ A:1267 C:191 G:216 T:1208 ] length 13 :[ A:1813 C:255 G:260 T:1805 ] length 12 :[ A:2702 C:353 G:353 T:2800 ] length 11 :[ A:4209 C:380 G:404 T:4184 ] length 10 :[ A:7181 C:446 G:428 T:7343 ] length 9 :[ A:9964 C:386 G:437 T:10011 ] length 8 :[ A:14581 C:699 G:601 T:14514 ] length 7 :[ A:28336 C:2656 G:2644 T:28782 ] length 6 :[ A:90274 C:11644 G:11543 T:89663 ] length 5 :[ A:308601 C:52038 G:52017 T:309011 ] length 4 :[ A:889188 C:199827 G:200919 T:885567 ] length 3 :[ A:2424590 C:938297 G:935629 T:2422964 ] length 2 :[ A:6232754 C:4721693 G:4718156 T:6219367 ]

As you can see, at lengths over 16, they are still a fairly frequent occurence. And even at lengths > 32, there are still enough to be worrying.


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