Agreed - but it wasn't entirely clear from the original question that this was the purpose of the calculation. Assuming that is the case then it surely behoves subscribers as far as possible to ask the right questions, or at least explain their reasons for needing to perform the calculation: it should not be assumed that others will understand what you meant to say, as opposed to what you did say!
If restraints are to be included then a rough estimate is to say that Nrestraints = Nparameters; a more precise estimate that I use is Nrestraints = 0.96 Nparameters, so as you say you need to add that to the reflection count. The rationale for this is that if 2 or more restraints have the same or nearly the same effect, i.e. they are not independent, then they should be counted as only 1 restraint, and if there are more restraints than parameters (i.e. more equations than unknowns) then they cannot all be independent, so Nparameters is the maximum possible value of Nrestraints, counting only independent restraints. In that situation the model would be completely defined by the restraints (and there would be no need for X-ray data!). In reality the parameters of the model are undefined to the extent that the molecules can freely translate & rotate (in general 6 params per molecule, or 3 for single atoms such as waters), and also for a protein the main-chain phi & psi angles (and sometimes side-chain chi angles) are undefined. So Nrestraints turns out to be slightly < Nparameters, in practice I've found that 0.96 is a reasonable estimate. This is much easier than trying to count individual bond length, angle, planar, torsion, B factor (etc.) restraints. Cheers -- Ian > -----Original Message----- > From: Artem Evdokimov [mailto:[EMAIL PROTECTED] > Sent: 29 August 2008 13:47 > To: Ian Tickle > Subject: RE: [ccp4bb] Ratio of Number of Reflections to > Number of restrained Parameters > > Angle/bond/planarity restraints (because they are > experimentally determined > from prior data) should count as observations. > > Artem > > -----Original Message----- > From: CCP4 bulletin board [mailto:[EMAIL PROTECTED] On > Behalf Of Ian > Tickle > Sent: Thursday, August 28, 2008 9:16 PM > To: [email protected] > Subject: Re: [ccp4bb] Ratio of Number of Reflections to > Number of restrained > Parameters > > Hi Rajan > > You don't really need a program: e.g. if there are N non-H atoms > refined, then there are 4N params (isotropic B) or 9N > (aniso). TLS adds > 19 params per group to the isotropic count. You count unique > reflections. > > -- Ian > > > -----Original Message----- > > From: [EMAIL PROTECTED] > > [mailto:[EMAIL PROTECTED] On Behalf Of Rajan Pillai > > Sent: 29 August 2008 00:35 > > To: [email protected] > > Subject: Ratio of Number of Reflections to Number of > > restrained Parameters > > > > Hi All, > > > > I was wondering if there is any program that calculates the > > ratio of number of reflections (observation) to number of > > restrained parameters. If not then how it can be calculated. > > The number of reflections is it number of unique reflections > > or number of the total reflections? > > > > Thanks, > > > > Rajan > > > > > > > Disclaimer > This communication is confidential and may contain privileged > information > intended solely for the named addressee(s). It may not be > used or disclosed > except for the purpose for which it has been sent. 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