# [Bioperl-l] calculate the frequency of occurrence of the mostcommonly observed amino acid at each position of multiplesequence alignment

Mark A. Jensen maj at fortinbras.us
Sat Feb 7 16:46:25 UTC 2009

```Yikes! Sounds like the authors need to pump some Perl too!
cheers MAJ
----- Original Message -----
From: Dylan Krishnan
To: Mark A. Jensen
Cc: bioperl-l at lists.open-bio.org
Sent: Saturday, February 07, 2009 11:43 AM
Subject: Re: [Bioperl-l] calculate the frequency of occurrence of the mostcommonly observed amino acid at each position of multiplesequence alignment

thanks mark!

the authors other approach is to load the alignment into a MS Excel worksheet and use the "autofilter" procedure to count the occurrences of any residue position of the alignment. the claim is "that excel is uselful for this purpose."sounds reasonable for 10 alignments but not 2000!

again, many thanks.

-dylan

On Sat, Feb 7, 2009 at 10:25 AM, Mark A. Jensen <maj at fortinbras.us> wrote:

Dylan,

This is an extremely good exercise for anyone learning Perl to do bioinformatics.
When you have done many exercises like this, you will see what people mean
when they say it is very straightforward.

Here are some hints:

Use the "entropy" scrap at http://www.bioperl.org/wiki/Site_entropy_in_an_alignment .
You will convert the function entropy_by_column() into the function you need.
Replace the line

\$ent{\$col} = entropy(values %res);

with a line you will write using the "hash key at max value" scrap, found
here: http://www.bioperl.org/wiki/Hash_key_at_the_max_value .

Happy coding!
Mark

----- Original Message ----- From: "Dylan Krishnan" <dylankrishnan at gmail.com>
To: <bioperl-l at lists.open-bio.org>
Sent: Saturday, February 07, 2009 11:10 AM
Subject: [Bioperl-l] calculate the frequency of occurrence of the mostcommonly observed amino acid at each position of multiplesequence alignment

I am new to perl but this is somethign I am seeking to do either through a
bioperl module or just perl. Apparently, this is quite "straightforward
using PERL," but I beg to differ.

Any assistance regarding this matter would be greatly appreciated.

Thanks!

-dylan

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