Re: [PyMOL] Possible to select the nth residue?

[Dan K. <dw...@ma...>]

Sorry the below actually won't work, you'll need something more...

nth_residue = 3
previous = -1
cur_res  = 0
nth_resi = 0
for at in cmd.get_model("molecule1 and chainA").atom:
    if (at.resi != previous):
         cur_res++

    if (cur_res == nth_residue):
         nth_resi = at.resi
         break

# Now do the selection...
cmd.select("myselection", "molecule1 and chain A and resi %s" % (nth_resi))


There might be a cleaner way, but something along these lines should work.

Sorry for the first email,
Dan

This looks better. However you'll want to put it in a script, wrap it 
with a function, etc...  I haven't test the above though.


Dan Kulp wrote:
> I just needed to do this and this was my solution
>
> NTH_RESIDUE=3
> cmd.select("myselection", "molecule1 and chain A and resi %s" % 
> (cmd.get_model("molecule1 and chain A").atom[NTH_RESIDUE]))
>
> will create a selection named myselection and contain only the 
> NTH_RESIDUE of molecule1 and chain  A.
>
> Hope this helps,
> ~Dan
>
> Alex Luso wrote:
>>   One more question.
>>
>>   Someone asked me this: is it possible in Pymol to select
>> the nth (e.g. the 3rd) residue in a molecule/chain without
>> knowing the pdb residue # itself?
>>
>>   -Alex
>>
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-- 
   Dan Kulp
   Biophysics Graduate Student @ UPenn
   dw...@ma...
   http://dwkulp.homelinux.net/tiki/tiki-index.php
--