Matching elements from 2 arrays in perl - perl

Right now I am attempting to synchronize two data files that are listed by date so that i can make comparisons later on. However I can not seem to print out only the lines where the dates match. At this point I have separated out the data for each file into 2 arrays. I need to find only the dates that are in both arrays and print them out. Any suggestions would be much appreciated.
Here is a sample set of the raw data that I am working with, each file is in the same format:
09/11/2009,00:56:00,51.602,47.894,87,88,0,1032
09/12/2009,00:56:00,57.794,55.796,93,54,0,1023.6
09/13/2009,00:56:00,64.292,62.204,93,66,0,1014.4
09/14/2009,00:56:00,61.592,55.4,80,25,0,1009.6
09/15/2009,00:56:00,58.604,53.798,84,31,0,1009.1
09/16/2009,00:56:00,53.6,48.902,84,45,0,1017
I have split the date into an array for each file. My ultimate goal is to only print lines of code where both files have data. So to do this I wanted to compare the 2 arrays with the elements being the dates.
My initial code looked like this:
foreach $bdate(#bdate){
while (<PL>){
chomp;
#arr = split (/,/);
$pday=$arr[1];
push #pdate, $pday;
if ($bdate eq $pdate){
print "$bdate,$pday\n";
}
}

One way (of many) would be to iterate once through each array, building a hash as follows;
for (#array1, #array2) {
$dates{$_}++;
}
Then you can print the keys that correspond to values of 2 or more;
print $_,"\n" for grep {$dates{$_} > 1} keys %dates;
(untested, written on a machine with no perl)
...and a quick CPAN search turns up List::Compare, with this example;
$lc = List::Compare->new(\#Llist, \#Rlist);
#intersection = $lc->get_intersection;

Here's example from perlfaq4 (simplified a bit):
my (#intersection, %count);
for my $element (#array1, #array2) { $count{$element}++ }
for my $element (keys %count) {
push #intersection, $element if $count{$element} > 1;
}
More idiomatic version:
my (%union, %isect);
for my $e (#array1, #array2) { $union{$e}++ && $isect{$e}++ }
my #intersection = keys %isect;
Both methods assume that each element is unique in a given array.

Related

i want to merge multiple csv files by specific condition using perl

i have multiple csv files, i want to merge all those files.....
i am showing some of my sample csv files below...
M1DL1_Interpro_sum.csv
IPR017690,Outer membrane, omp85 target,821
IPR014729,Rossmann,327
IPR013785,Aldolase,304
IPR015421,Pyridoxal,224
IPR003594,ATPase,179
IPR000531,TonB receptor,150
IPR018248,EF-hand,10
M1DL2_Interpro_sum.csv
IPR017690,Outer membrane, omp85 target,728
IPR013785,Aldolase,300
IPR014729,Rossmann,261
IPR015421,Pyridoxal,189
IPR011991,Winged,113
IPR000873,AMP-dependent synthetase/ligase,111
M1DL3_Interpro_sum.csv
IPR017690,Outer membrane,905
IPR013785,Aldolase,367
IPR014729,Rossmann,338
IPR015421,Pyridoxal,271
IPR003594,ATPase,158
IPR018248,EF-hand,3
now to merge these files i have tried the following code
#ARGV = <merge_csvfiles/*.csv>;
print #ARGV[0],"\n";
open(PAGE,">outfile.csv") || die"Can't open outfile.csv\n";
while($i<scalar(#ARGV))
{
open(FILE,#ARGV[$i]) || die"Can't open ...#ARGV[$i]...\n";
$data.=join("",<FILE>);
close FILE;
print"file completed...",$i+1,"\n";
$i++;
}
#data=split("\n",$data);
#data2=#data;
print scalar(#data);
for($i=0;$i<scalar(#data);$i++)
{
#id1=split(",",#data[$i]);
$id_1=#id1[0];
#data[$j]=~s/\n//;
if(#data[$i] ne "")
{
print PAGE "\n#data[$i],";
for($j=$i+1;$j<scalar(#data2);$j++)
{
#id2=split(",",#data2[$j]);
$id_2=#id2[0];
if($id_1 eq $id_2)
{
#data[$j]=~s/\n//;
print PAGE "#data2[$j],";
#data2[$j]="";
#data[$j]="";
print "match found at ",$i+1," and ",$j+1,"\n";
}
}
}
print $i+1,"\n";
}
merge_csvfiles is a folder which contains all the files
output of above code is
IPR017690,Outer membrane,821,IPR017690,Outer membrane ,728,IPR017690,Outer membrane,905
IPR014729,Rossmann,327,IPR014729,Rossmann,261,IPR014729,Rossmann,338
IPR013785,Aldolase,304,IPR013785,Aldolase,300,IPR013785,Aldolase,367
IPR015421,Pyridoxal,224,IPR015421,Pyridoxal,189,IPR015421,Pyridoxal,271
IPR003594,ATPase,179,IPR003594,ATPase,158
IPR000531,TonB receptor,150
IPR018248,EF-hand,10,IPR018248,EF-hand,3
IPR011991,Winged,113
IPR000873,AMP-dependent synthetase/ligase
but i want the output in following format....
IPR017690,Outer membrane,821,IPR017690,Outer membrane ,728,IPR017690,Outer membrane,905
IPR014729,Rossmann,327,IPR014729,Rossmann,261,IPR014729,Rossmann,338
IPR013785,Aldolase,304,IPR013785,Aldolase,300,IPR013785,Aldolase,367
IPR015421,Pyridoxal,224,IPR015421,Pyridoxal,189,IPR015421,Pyridoxal,271
IPR003594,ATPase,179,0,0,0,IPR003594,ATPase,158
IPR000531,TonB receptor,150,0,0,0,0,0,0
IPR018248,EF-hand,10,0,0,0,IPR018248,EF-hand,3
0,0,0,IPR011991,Winged,113,0,0,0
0,0,0,IPR000873,AMP-dependent synthetase/ligase,111,0,0,0
Has anybody got any idea how can i do this?
Thank you for the help
As mentioned in Miguel Prz's comment, you haven't explained how you want the merge to be performed, but, judging by the "desired output" sample, it appears that what you want is to concatenate lines with matching IDs from all three input files into a single line in the output file, with "0,0,0" taking the place of any lines which don't appear in a given file.
So, then:
#!/usr/bin/env perl
use strict;
use warnings;
my #input_files = glob 'merge_csvfiles/*.csv';
my %data;
for my $i (0 .. $#input_files) {
open my $infh, '<', $input_files[$i]
or die "Failed to open $input_files[$i]: $!";
while (<$infh>) {
chomp;
my $id = (split ',', $_, 2)[0];
$data{$id}[$i] = $_;
}
print "Input file read: $input_files[$i]\n";
}
open my $outfh, '>', 'outfile.csv' or die "Failed to open outfile.csv: $!";
for my $id (sort keys %data) {
my #merge_data;
for my $i (0 .. $#input_files) {
push #merge_data, $data{$id}[$i] || '0,0,0';
}
print $outfh join(',', #merge_data) . "\n";
}
The first loop collects all the lines from each file into a hash of arrays. The hash keys are the IDs, so the lines for that ID from all files are kept together, and the value for each key is (a reference to) an array of the line associated with that ID in each file; using an array for this allows us to keep track of values which are missing as well as those which are present.
The second loop then takes the keys of that hash (in alphabetical order) and, for each one, creates a temporary array of the values associated with that ID, substituting "0,0,0" for missing values, joins them into a single string, and prints that to the output file.
The results, in outfile.csv, are:
IPR000531,TonB receptor,150,0,0,0,0,0,0
0,0,0,IPR000873,AMP-dependent synthetase/ligase,111,0,0,0
IPR003594,ATPase,179,0,0,0,IPR003594,ATPase,158
0,0,0,IPR011991,Winged,113,0,0,0
IPR013785,Aldolase,304,IPR013785,Aldolase,300,IPR013785,Aldolase,367
IPR014729,Rossmann,327,IPR014729,Rossmann,261,IPR014729,Rossmann,338
IPR015421,Pyridoxal,224,IPR015421,Pyridoxal,189,IPR015421,Pyridoxal,271
IPR017690,Outer membrane, omp85 target,821,IPR017690,Outer membrane, omp85 target,728,IPR017690,Outer membrane,905
IPR018248,EF-hand,10,0,0,0,IPR018248,EF-hand,3
Edit: Added explanations requested by OP in comments
can u expalain me the working of my $id = (split ',', $_, 2)[0]; and $# in this program
my $id = (split ',', $_, 2)[0]; gets the text prior to the first comma in the last line of text that was read:
Because I didn't specify what variable to put the data in, while (<$infh>) reads it into the default variable $_.
split ',', $_, 2 splits up the value of $_ into a list of comma-separated fields. The 2 at the end tells it to only produce at most 2 fields; the code will work fine without the 2, but, since I only need the first field, splitting into more parts isn't necessary.
Putting (...)[0] around the split command turns the returned list of fields into an (anonymous) array and returns the first element of that array. It's the same as if I'd written my #fields = split ',', $_, 2; my $id = $fields[0];, but shorter and without the extra variable.
$#array returns the highest-numbered index in the array #array, so for my $i (0 .. $#array) just means "loop over the indexes for all elements in #array". (Note that, if I hadn't needed the value of the index counter, I would have instead looped over the array's data directly, by using for my $filename (#input_files), but it would have been less convenient to keep track of the missing values if I'd done it that way.)

Perl need the right grep operator to match value of variable

I want to see if I have repeated items in my array, there are over 16.000 so will automate it
There may be other ways but I started with this and, well, would like to finish it unless there is a straightforward command. What I am doing is shifting and pushing from one array into another and this way, check the destination array to see if it is "in array" (like there is such a command in PHP).
So, I got this sub routine and it works with literals, but it doesn't with variables. It is because of the 'eq' or whatever I should need. The 'sourcefile' will contain one or more of the words of the destination array.
// Here I just fetch my file
$listamails = <STDIN>;
# Remove the newlines filename
chomp $listamails;
# open the file, or exit
unless ( open(MAILS, $listamails) ) {
print "Cannot open file \"$listamails\"\n\n";
exit;
}
# Read the list of mails from the file, and store it
# into the array variable #sourcefile
#sourcefile = <MAILS>;
# Close the handle - we've read all the data into #sourcefile now.
close MAILS;
my #destination = ('hi', 'bye');
sub in_array
{
my ($destination,$search_for) = #_;
return grep {$search_for eq $_} #$destination;
}
for($i = 0; $i <=100; $i ++)
{
$elemento = shift #sourcefile;
if(in_array(\#destination, $elemento))
{
print "it is";
}
else
{
print "it aint there";
}
}
Well, if instead of including the $elemento in there I put a 'hi' it does work and also I have printed the value of $elemento which is also 'hi', but when I put the variable, it does not work, and that is because of the 'eq', but I don't know what else to put. If I put == it complains that 'hi' is not a numeric value.
When you want distinct values think hash.
my %seen;
#seen{ #array } = ();
if (keys %seen == #array) {
print "\#array has no duplicate values\n";
}
It's not clear what you want. If your first sentence is the only one that matters ("I want to see if I have repeated items in my array"), then you could use:
my %seen;
if (grep ++$seen{$_} >= 2, #array) {
say "Has duplicates";
}
You said you have a large array, so it might be faster to stop as soon as you find a duplicate.
my %seen;
for (#array) {
if (++$seen{$_} == 2) {
say "Has duplicates";
last;
}
}
By the way, when looking for duplicates in a large number of items, it's much faster to use a strategy based on sorting. After sorting the items, all duplicates will be right next to each other, so to tell if something is a duplicate, all you have to do is compare it with the previous one:
#sorted = sort #sourcefile;
for (my $i = 1; $i < #sorted; ++$i) { # Start at 1 because we'll check the previous one
print "$sorted[$i] is a duplicate!\n" if $sorted[$i] eq $sorted[$i - 1];
}
This will print multiple dupe messages if there are multiple dupes, but you can clean it up.
As eugene y said, hashes are definitely the way to go here. Here's a direct translation of the code you posted to a hash-based method (with a little more Perlishness added along the way):
my #destination = ('hi', 'bye');
my %in_array = map { $_ => 1 } #destination;
for my $i (0 .. 100) {
$elemento = shift #sourcefile;
if(exists $in_array{$elemento})
{
print "it is";
}
else
{
print "it aint there";
}
}
Also, if you mean to check all elements of #sourcefile (as opposed to testing the first 101 elements) against #destination, you should replace the for line with
while (#sourcefile) {
Also also, don't forget to chomp any values read from a file! Lines read from a file have a linebreak at the end of them (the \r\n or \n mentioned in comments on the initial question), which will cause both eq and hash lookups to report that otherwise-matching values are different. This is, most likely, the reason why your code is failing to work correctly in the first place and changing to use sort or hashes won't fix that. First chomp your input to make it work, then use sort or hashes to make it efficient.

Iterating over data structure

I am trying to iterate over this data structure:
$deconstructed->{data}->{workspaces}[0]->{workspace}->{facts}[0]->{code}
where fact[0] is increasing. It's several files I am processing so the number of {facts}[x] varies.
I thought this might work but it doesn't seem to be stepping up the $iter var:
foreach $iter(#{$deconstructed->{data}->{workspaces}[0]->{workspace}->{facts}}){
print $deconstructed->{data}->{workspaces}[0]->{workspace}->{facts}[$iter]->{code}."\n";
}
I'm totally digging data structures but this one is stumping me. Any advice what might be wrong here?
$iter is being set to the content of each item in the array not the index. e.g.
my $a = [ 'a', 'b', 'c' ];
for my $i (#$a) {
print "$i\n";
}
...prints:
a
b
c
Try:
foreach $iter (#{$deconstructed->{data}->{workspaces}[0]->{workspace}->{facts}}){
print $iter->{code}."\n";
}
$iter is not going to be an index that you can subscript the array with, it is rather the current element of the array. So I guess you should be fine with:
$iter->{code}
Your $iter contains the data sctructure. What you basiclly want is:
foreach my $elem ( #{$deconstructed->{data}->{workspaces}[0]->{workspace}->{facts}} ){
print $elem->{code};
}
or:
foreach my $iter ( 0 .. scalar #{$deconstructed->{data}->{workspaces}[0]->{workspace}->{facts}} ){
print $deconstructed->{data}->{workspaces}[0]->{workspace}->{facts}[$iter]->{code}."\n";
}
Since you are looping over the array, your misnamed $iter is the value you are looking for, not an index.
If you want to loop over the indexes instead, do:
foreach $iter ( 0 .. $#{$deconstructed->{data}->{workspaces}[0]->{workspace}->{facts}} ) {
print "Index $iter: ",
$deconstructed->{data}->{workspaces}[0]->{workspace}->{facts}[$iter]->{code}."\n";
}
Also note that you can drop -> between two [] or {}:
$deconstructed->{data}{workspaces}[0]{workspace}{facts}[$iter]{code}
I recommend reading http://perlmonks.org/?node=References+quick+reference.
When you have ugly data structures like this, make an interface for it so your life is easier:
foreach my $fact ( $data_obj->facts ) { # make some lightweight class for this
....;
}
Even without that, consider using a reference to just the part of the data structure you need so you don't think about the rest:
my $facts = $deconstructed->{data}{workspaces}[0]{workspace}{facts};
foreach my $fact ( #$facts ) {
print "Thing is $fact->{code}\n";
}
It's just a reference, so you're not recreating anything. Since you only have to think about the parts beyond the facts key, the problem doesn't look as hard.

perl Get indexes of matches in array

I want to search for an element in an array. What I want to get from this search is the all the indices of the array where I find a match.
So, for example the word I want to search is :
$myWord = cat
#allMyWords = my whole file with multiple occurrences of cat in random positions in file
So, if cat occurs at 3rd, 19th and 110th position, I want those indices as a result of it. I was wondering if there is a small and simple method to do this.
Thanks!
With List::MoreUtils:
use List::MoreUtils qw(indexes);
my #indexes = indexes { $_ eq 'cat' } #words;
If you haven't read the file yet, you can read it using "slurp mode":
local $/; # enable slurp mode
my #words = split(/\s+/, <>);
I got the answer. This is the code that will return all the indices in the array where an element we are searching for is found.
my( #index )= grep { $allMyWords[$_] eq $word } 0..$#allMyWords;
print "Index : #index\n";

Why does my Perl for loop exit early?

I am trying to get a perl loop to work that is working from an array that contains 6 elements. I want the loop to pull out two elements from the array, perform certain functions, and then loop back and pull out the next two elements from the array until the array runs out of elements. Problem is that the loop only pulls out the first two elements and then stops. Some help here would be greatly apperaciated.
my open(infile, 'dnadata.txt');
my #data = < infile>;
chomp #data;
#print #data; #Debug
my $aminoacids = 'ARNDCQEGHILKMFPSTWYV';
my $aalen = length($aminoacids);
my $i=0;
my $j=0;
my #matrix =();
for(my $i=0; $i<2; $i++){
for( my $j=0; $j<$aalen; $j++){
$matrix[$i][$j] = 0;
}
}
The guidelines for this program states that the program should ignore the presence of gaps in the program. which means that DNA code that is matched up with a gap should be ignored. So the code that is pushed through needs to have alignments linked with gaps removed.
I need to modify the length of the array by two since I am comparing two sequence in this part of the loop.
#$lemseqcomp = $lenarray / 2;
#print $lenseqcomp;
#I need to initialize these saclar values.
$junk1 = " ";
$junk2 = " ";
$seq1 = " ";
$seq2 = " ";
This is the loop that is causeing issues. I belive that the first loop should move back to the array and pull out the next element each time it loops but it doesn't.
for($i=0; $i<$lenarray; $i++){
#This code should remove the the last value of the array once and
#then a second time. The sequences should be the same length at this point.
my $last1 =pop(#data1);
my $last2 =pop(#data1);
for($i=0; $i<length($last1); $i++){
my $letter1 = substr($last1, $i, 1);
my $letter2 = substr($last2, $i, 1);
if(($letter1 eq '-')|| ($letter2 eq '-')){
#I need to put the sequences I am getting rid of somewhere. Here is a good place as any.
$junk1 = $letter1 . $junk1;
$junk2 = $letter1 . $junk2;
}
else{
$seq1 = $letter1 . $seq1;
$seq2 = $letter2 . $seq2;
}
}
}
print "$seq1\n";
print "$seq2\n";
print "#data1\n";
I am actually trying to create a substitution matrix from scratch and return the data. The reason why the code looks weird, is because it isn't actually finished yet and I got stuck.
This is the test sequence if anyone is curious.
YFRFR
YF-FR
FRFRFR
ARFRFR
YFYFR-F
YFRFRYF
First off, if you're going to work with sequence data, use BioPerl. Life will be so much easier. However...
Since you know you'll be comparing the lines from your input file as pairs, it makes sense to read them into a datastructure that reflects that. As elsewhere suggested, an array like #data[[line1, line2],[line3,line4]) ensures that the correct pairs of lines are always together.
What I'm not clear on what you're trying to do is:
a) are you generating a consensus
sequence where the 2 sequences are
difference only by gaps
b) are your 2 sequences significantly
different and you're trying to
exclude the non-aligning parts and
then generate a consensus?
So, does the first pair represent your data, or is it more like the second?
ATCG---AAActctgGGGGG--taGC
ATCGcccAAActctgGGGGGTTtaGC
ATCG---AAActctgGGGGG--taGCTTTTTTTTTTTTTTTTTTTTTTTTTTTTTT
ATCGcccAAActctgGGGGGTTtaGCGGGGGGGGGGGGGGGGGGGGGGGGGGGGGG
The problem is that you're using $i as the counter variable for both your loops, so the inner loop modifies the counter out from under the outer loop. Try changing the inner loop's counter to $j, or using my to localize them properly.
Don't store your values as an array, store as a two-dimensional array:
my #dataset = ([$val1, $val2], [$val3, $val4]);
or
my #dataset;
push (#dataset, [$val_n1, $val_n2]);
Then:
for my $value (#dataset) {
### Do stuff with $value->[0] and $value->[1]
}
There are lots of strange things in your code: you are initializing a matrix then not using it; reading a whole file into an array; scanning a string C style but then not doing anything with the unmatched values; and finally, just printing the two last processed values (which, in your case, are the two first elements of your array, since you are using pop.)
Here's a guess.
use strict;
my $aminoacids = 'ARNDCQEGHILKMFPSTWYV';
# Preparing a regular expression. This is kind of useful if processing large
# amounts of data. This will match anything that is not in the string above.
my $regex = qr([^$aminoacids]);
# Our work function.
sub do_something {
my ($a, $b) = #_;
$a =~ s/$regex//g; # removing unwanted characters
$b =~ s/$regex//g; # ditto
# Printing, saving, whatever...
print "Something: $a - $b\n";
return ($a, $b);
}
my $prev;
while (<>) {
chomp;
if ($prev) {
do_something($prev, $_);
$prev = undef;
} else {
$prev = $_;
}
}
print STDERR "Warning: trailing data: $prev\n"
if $prev;
Since you are a total Perl/programming newbie, I am going to show a rewrite of your first code block, then I'll offer you some general advice and links.
Let's look at your first block of sample code. There is a lot of stuff all strung together, and it's hard to follow. I, personally, am too dumb to remember more than a few things at a time, so I chop problems into small pieces that I can understand. This is (was) known as 'chunking'.
One easy way to chunk your program is use write subroutines. Take any particular action or idea that is likely to be repeated or would make the current section of code long and hard to understand, and wrap it up into a nice neat package and get it out of the way.
It also helps if you add space to your code to make it easier to read. Your mind is already struggling to grok the code soup, why make things harder than necessary? Grouping like things, using _ in names, blank lines and indentation all help. There are also conventions that can help, like making constant values (values that cannot or should not change) all capital letters.
use strict; # Using strict will help catch errors.
use warnings; # ditto for warnings.
use diagnostics; # diagnostics will help you understand the error messages
# Put constants at the top of your program.
# It makes them easy to find, and change as needed.
my $AMINO_ACIDS = 'ARNDCQEGHILKMFPSTWYV';
my $AMINO_COUNT = length($AMINO_ACIDS);
my $DATA_FILE = 'dnadata.txt';
# Here I am using subroutines to encapsulate complexity:
my #data = read_data_file( $DATA_FILE );
my #matrix = initialize_matrix( 2, $amino_count, 0 );
# now we are done with the first block of code and can do more stuff
...
# This section down here looks kind of big, but it is mostly comments.
# Remove the didactic comments and suddenly the code is much more compact.
# Here are the actual subs that I abstracted out above.
# It helps to document your subs:
# - what they do
# - what arguments they take
# - what they return
# Read a data file and returns an array of dna strings read from the file.
#
# Arguments
# data_file => path to the data file to read
sub read_data_file {
my $data_file = shift;
# Here I am using a 3 argument open, and a lexical filehandle.
open( my $infile, '<', $data_file )
or die "Unable to open dnadata.txt - $!\n";
# I've left slurping the whole file intact, even though it can be very inefficient.
# Other times it is just what the doctor ordered.
my #data = <$infile>;
chomp #data;
# I return the data array rather than a reference
# to keep things simple since you are just learning.
#
# In my code, I'd pass a reference.
return #data;
}
# Initialize a matrix (or 2-d array) with a specified value.
#
# Arguments
# $i => width of matrix
# $j => height of matrix
# $value => initial value
sub initialize_matrix {
my $i = shift;
my $j = shift;
my $value = shift;
# I use two powerful perlisms here: map and the range operator.
#
# map is a list contsruction function that is very very powerful.
# it calls the code in brackets for each member of the the list it operates against.
# Think of it as a for loop that keeps the result of each iteration,
# and then builds an array out of the results.
#
# The range operator `..` creates a list of intervening values. For example:
# (1..5) is the same as (1, 2, 3, 4, 5)
my #matrix = map {
[ ($value) x $i ]
} 1..$j;
# So here we make a list of numbers from 1 to $j.
# For each member of the list we
# create an anonymous array containing a list of $i copies of $value.
# Then we add the anonymous array to the matrix.
return #matrix;
}
Now that the code rewrite is done, here are some links:
Here's a response I wrote titled "How to write a program". It offers some basic guidelines on how to approach writing software projects from specification. It is aimed at beginners. I hope you find it helpful. If nothing else, the links in it should be handy.
For a beginning programmer, beginning with Perl, there is no better book than Learning Perl.
I also recommend heading over to Perlmonks for Perl help and mentoring. It is an active Perl specific community site with very smart, friendly people who are happy to help you. Kind of like Stack Overflow, but more focused.
Good luck!
Instead of using a C-style for loop, you can read data from an array two elements at a time using splice inside a while loop:
while (my ($letter1, $letter2) = splice(#data, 0, 2))
{
# stuff...
}
I've cleaned up some of your other code below:
use strict;
use warnings;
open(my $infile, '<', 'dnadata.txt');
my #data = <$infile>;
close $infile;
chomp #data;
my $aminoacids = 'ARNDCQEGHILKMFPSTWYV';
my $aalen = length($aminoacids);
# initialize a 2 x 21 array for holding the amino acid data
my $matrix;
foreach my $i (0 .. 1)
{
foreach my $j (0 .. $aalen-1)
{
$matrix->[$i][$j] = 0;
}
}
# Process all letters in the DNA data
while (my ($letter1, $letter2) = splice(#data, 0, 2))
{
# do something... not sure what?
# you appear to want to look up the letters in a reference table, perhaps $aminoacids?
}