This proposal is for a standard_name for the real/imaginary
component, i.e. a way of coding complex data in a standard way --
talking about amplitude/phase is a total red herring, and fourier
transform was merely an example, again, not the proposal.
The fact remains that all software that is trea
Dear Bryan
I may have overemphasised the point that you might be interested in only one
of the amplitude and phase. My main point is you might want to express a FT
as amplitude and phase, rather than real and imaginary. Since amplitude and
phase don't have the same units, I think it would be again
Hi Jonathan
I wasn't thinking about amp and phase, primarily because I had a specific
use case in mind (as you appear to do, so that's both of us :-)
I concede that you can make an argument that in *some* cases you might
only use one component from amp and phase, but I can't think of any
mains
Dear Bryan and Benno
> I do *not* think it is appropriate to split the real and imaginary parts
> into two variables, since one almost never uses just one or the other,
> so it's a rather different case from splitting vector components.
I disagree still. Fourier transforms don't have to express
Hi Benno, Jonathan
Ok, now I think you're both right :-) but I fancy muddying the water
some.
I do *not* think it is appropriate to split the real and imaginary parts
into two variables, since one almost never uses just one or the other,
so it's a rather different case from splitting vector co
Hi Bryan,
Thanks for chiming in -- your comments are quite helpful.
As for
On Thu, Jun 24, 2010 at 6:45 AM, Bryan Lawrence
wrote:
> However, despite the discussion thus far, I'm not entirely sure I
> understand exactly what Benno is proposing, not least because there are
> different ways of ar
Hi Folks
I've not been following this in as much detail as I'd like, but I'd make
the observation that the change from
- physical quantity on a physical grid to
- a fourier transform (in one or more spatial dimensions) to
- spherical harmonics
hasn't changed *what* is measured, nor where, it
Dear Brian
> Isn't the use of "cell_methods" with a value of "variance" an example where
> we don't require a different standard_name even though the units are
> different?
Yes. I simplified what I said in order not to be confusing, but perhaps the
result was confusing! Cell methods specifies sta
Hi Jonathan,
I'm wondering about this statement:
> I don't think it's misleading. This is a consistent rule in CF standard
> names: quantities with different canonical units must have different standard
> names.
Isn't the use of "cell_methods" with a value of "variance" an example where
we don't
Dear Benno
I think our arguments are all reasonable and clearly stated. The conclusion
is not clear. Other points of view would be useful.
> 1) Fourier transform is a change of basis, not physical variable -- it
> is invertible as a matter of fact, as long as you keep the real and
> imaginary par
Clearly stated, wish I could return the favor.
However,
1) Fourier transform is a change of basis, not physical variable -- it
is invertible as a matter of fact, as long as you keep the real and
imaginary parts. Because it is a change of basis, it is much more
analagous to a projection transfor
Dear Benno
> This time you have understood
Good.
> I believe my proposal is a lot more useful.
Our proposals differ in two ways:
* I suggest the standard name should not be air_pressure, but should include
a phrase like fourier_transform_of_air_pressure_wrt_time. Basically that's
because if you
This time you have understood, and I believe my proposal is a lot more useful.
Benno
On Mon, Jun 14, 2010 at 1:42 PM, Jonathan Gregory
wrote:
> Dear Benno
>
> You mean C is either "real" or "imaginary"? I think the CF-like way to do
> this would be to have two different data variables for it, on
I am sorry, you misunderstand me: I am looking for the standard_name
to label the coordinate variable that corresponds to real and
imaginary parts, not the non-coordinate-variable that has real and
imaginary parts.
For example, If I had a Fourier transform of 3d air_pressure, it
would be a real
Dear Benno
You mean C is either "real" or "imaginary"? I think the CF-like way to do
this would be to have two different data variables for it, one for the real
part, one for the imaginary. That's like having different standard names
for spatial components, as we do, rather than dimensions for com
Dear Benno
In a standard name, more information is needed, to identify the quantity whose
real and imaginary parts you want to name.
Best wishes
Jonathan
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Hello All,
We have made some use of having a coordinate-variable that corresponds
to real and imaginary parts, for outputs of Fourier transforms, for
example. We usually tag this name "C" and long_name="complex", and
give it values of "R" and "I", but it would be appropriate to tag it
with a st
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