Hi Rasmus,
I had in mind mainly your first scenario, and your solutions are
certainly viable. I guess I'm just used to being able to do referencing
either way with a single command. Perhaps I should stop being so lazy?
Chris
On Thu, 2005-02-24 at 12:16, Rasmus Fogh wrote:
> Dear All,
>
> Just back from a short holiday:
>
> I really do not think this is the way to go. A peak represents a maximum
> in the actual spectrum. If you change referencing while keeping the ppm
> values constant you will move the peaks away from the maximum they are
> supposed to represent. The whole point of storing peaks in points rather
> than ppm was to avoid having this kind of problem when you change your
> referencing. Adding a command to change referencing while keeping the peak
> ppm values gives people a tempting opportunity to make mistakes, without,
> in my opinion, adding much.
>
> I can see only two cases where this might be releavnt
>
> - One is if you copy peaks (correctly - in ppm) from one spectrum to
> another, and then find that the spectra were not quite with the same
> reference. The obvious solution would be to delete the peaks, fix the
> referencing, and copy the peaks again, or to run a little script that
> moves the peaks. We can write one - and doing it that way should make it
> clearer to the user what is going on.
>
> - The other case is if you copy peaks (incorrectly - in points) to another
> spectrum, and find they do not fit. Here, surely, the solution is to get
> the copying right in the first place, not to hack the result afterwards.
>
> Chris - can you suggest more precisely in what kind of situation you would
> want this kind of command? Maybe I have missed something, or maybe we
> could find another way of handling the problem.
>
> Yours,
>
> Rasmus
>
> ---------------------------------------------------------------------------
> Dr. Rasmus H. Fogh Email: [log in to unmask]
> Dept. of Biochemistry, University of Cambridge,
> 80 Tennis Court Road, Cambridge CB2 1GA, UK. FAX (01223)766002
>
> On Thu, 17 Feb 2005, Wayne Boucher wrote:
>
> > Right, I've added something into the "edit spectrum reference" popup which
> > lets you keep the peak ppm values unchanged when you change the
> > referencing (the default is still taht the peak point values remain
> > unchanged). (The way it's done the referencing information is changed, so
> > the peak ppms change, then the peak point values are adjusted so the ppm
> > goes back, so the screen effect is a bit amusing, with the peaks moving
> > and then moving back.) As usual, this will be in the next release.
> >
> > Wayne
> >
> > On Thu, 17 Feb 2005, Wayne Boucher wrote:
> >
> > > There is no easy way of doing this now but it sounds like we need an
> > > option in the "edit spectrum reference" popup which says "do you want peak
> > > positions fixed in points or ppm?" (is there any other alternative?).
> > > Since the positions are stored in points the "ppm" option would involve
> > > having to iterate over all the peaks updating the information, but that's
> > > not the end of the world.
> > >
> > > Wayne
> > >
> > > On Thu, 17 Feb 2005, Chris MacRaild wrote:
> > >
> > > > This behaviour makes sense in some some cases, but in other situations
> > > > it would be nice to be able to work the other way ie. to shift the
> > > > spectrum without changing the chemical shift of the peaks and associated
> > > > resonances. Is there an easy way of doing this, other than editing the
> > > > spectrum header and reloading?
> > > >
> > > > Thanks,
> > > > Chris
> > > >
> > > > On Thu, 2005-02-17 at 09:54, Wim Vranken wrote:
> > > > > Hi Andy,
> > > > >
> > > > > Peak positions in a spectrum are stored in points (not ppm) so if you
> > > > > rereference the spectrum, the peaks will change chemical shift value
> > > > > accordingly (i.e. the peak boxes will stay with the actual peaks in the
> > > > > spectrum).
> > > > >
> > > > > Bye,
> > > > >
> > > > > Wim
> > > > >
> > > >
> > >
> >
>
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