VMD-L Mailing List

From: Maxim Belkin (mbelkin_at_ks.uiuc.edu)
Date: Tue Sep 23 2014 - 09:38:09 CDT

How about "charge == -whatever" (without quotations)? It involves a couple of extra symbols, but it works.

Maxim

On Sep 23, 2014, at 9:08 AM, Josh Vermaas <vermaas2_at_illinois.edu> wrote:

> The negative sign. If you use charge "-0.7982", it'll work. John can probably be more enlightening about the details of WHY this is the case (I ran into this problem with negative resids, and I couldn't figure out why this was a problem), but the negative sign screws up the atomselection parser somehow unless its put in quotations. Note that negative numbers are allowed as math operands, so if you wanted charge > -0.8 and charge < -0.79, there the negative signs are handled correctly.
>
> -Josh Vermaas
> On 09/22/2014 09:25 PM, M Karim wrote:
>> Hi,
>>
>> I have different atom types in the structure, and found the easiest way to select them by their charges. In the selection menu, I can easily select atom types with positive charges. However, atoms with negative charges are not selected and I get this error:
>>
>> Unable to parse this atom selection.
>>
>>
>> I, for example, use this command in the Selected Atoms area:
>>
>> charge -0.798200
>>
>> The command window also shows:
>>
>> ERROR) syntax error
>>
>>
>> What is the problem with the syntax?
>>
>> Thank you.
>