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
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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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