2D FFT

On Feb 3, 6:37&#4294967295;pm, Rune Allnor <all...@tele.ntnu.no> wrote:
> On 3 Feb, 19:00, Chris Bore <chris.b...@gmail.com> wrote:
>
>
>
>
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> > On Feb 3, 6:44&#4294967295;am, Rune Allnor <all...@tele.ntnu.no> wrote:
>
> > > On 2 Feb, 18:06, Chris Bore <chris.b...@gmail.com> wrote:
>
> > > > I always teach in a way that
> > > > depends on powerful visual or auditory images.
>
> > > 'Infotainment.' A very dangerous method. In recent years I have
> > > started seeing on TV the movies and visualizations I made in my
> > > mind decades ago, when I read the books on geology and astronomy
> > > as a kid.
>
> > Yeah, that's what they say. :-)
>
> > But here is a question. Why would you avoid the use of images,
> > analogies, models and visualizations, when so many people do find them
> > helpful? To take your geology example, if I read about volcanoes I can
> > visualize for myself what one looks like and how it works, but why
> > would it be wrong for someone to show me a picture of one, or an
> > animation of the geolgic forces working on it?
>
> They are helpful as long as they don't dominate. The problem
> occurs if the students are releaved of the work of imagining
> what goes on.
>
>
>
>
>
> > > As far as I am concerned, the insight lies not in seeing the end
> > > visualization, but in interpreting and contemplating the material
> > > you read, to get there.
>
> > > > I hate equations and
> > > > formulae unless I can show some physically reasonable visualization of
> > > > what they mean. It drives some of my colleagues wild, because they can
> > > > 'see' from the formulae alone, whereas I am just a poor dumb slow
> > > > person who has to grope my way towards enlightenment using models and
> > > > analogies drawn from the world around me.
>
> > > Well, I might not have phrased it quite like that, but I have to
> > > agree with your colleagues. Learning to 'see' from an equation
> > > is not something that comes for free. It takes hard work over
> > > long time to learn. Students need to understand that, and get
> > > to work on it.
>
> > I'm lucky in that my 'students' are not in academia, but usually
> > practising engineers who did learn the 'right' way but without
> > understanding it. So they tend to be grateful for my dumbed down
> > approach that at least enables them to do their work. :-) So in a way
> > you could say I benefit from all the work that was put into them in
> > the 'right' way even though it never helped them in any practical way.
>
> OK. As long as that premise is fully understood by the students.
> And you are clear with them that what you tell them is an (over)
> simplification of the maths.
>
> > The other problem I do see with understanding through equations is,
> > they fail to see the limitations. For example some visualizations of
> > the basis functions for a 2D FT can help you to see easily how they
> > are poor models for certain types of 2D data, and how limitations
> > imposed by doing discrete math can change what you are seeing. Some of
> > these things may be quite hard to see so readily from the equations,
> > and so the equations may be over-relied upon. that is, the equations
> > can tend to be taken as the 'right' model with the real world coming
> > in a poor second. This is how, for example, we get such lousy digital
> > cameras because nobody seems to realise that a great big blob of light-
> > sensitive silicon is not a Dirac delta function.
>
> That's a direct consequence of the negligence of maths teaching
> in practical DSP an negligence of practical experience in academia:
> The practitioners don't understand the maths, and can neither
> understand nor criticize it, since they lack the training. The
> academics don't understand the problems caused by idealizations
> and simplifications of the models.
>
>
>
>
>
> > > While you personally might have found your preferred way of coping
> > > with maths, be aware that you set the stage for your students as
> > > well.
> > > It is a general rule in teaching that very few students can reach
> > > beyond the level of their teacher. Those very few who can, can only
> > > reach a limited distance beyond. So the infortainment shows might
> > > give a short-term illusion of progress, but it undermines the long-
> > > term results one usually strives for.
>
> > Now here I disagree totally. Not about infotainment but about
> > excelling beyond the teacher. Most of my students go well beyond what
> > I teach them, and that is the whole point. I know so little, what
> > would be the value in teaching them even less? And I am well impressed
> > by the ability of most engineers of all kinds to take what is taught
> > to them, question and internalise it, and then to go way beyond what
> > the teacher may ever have thought.
>
> I see the limitations, and have done for years. There aren't many
> practitioners out there who have the combination of academic and
> practical experience I have. Few academics have worked with data;
> few practitioners have studied the maths etc.
>
> I hit the wall when people insist on 'physical' or 'intuitive'
> explanations for the maths. This is caused solely by lack of
> training, and is *the* main obstacle that prevents DSP from
> progressing forward and not un around in circles as it is
> tending to, these days.

Well, here we will have to agree to differ. I require the math to
correspond to a practical model, for that model to be made explicit in
ways that are not reliant simply on the math itself, and for the model
to be tested against reality. But I do acknowledge that yours is by
far the majority opinion.

Also, I don't think this is caused by lack of training. I
misunderestimated myself when I said I was too dumb to do the math. I
have a PhD in DSP and 30 years experience working in the field, both
mathematically and practically. What I should have said is, that
through deepening my understanding of the maths and studying the
processes by which people learn in ways that enable them to apply
their knowledge, I have become convinced that it is essential to
complement the math with models and visualizations and that the math
on its own is insufficient to practical application. So the issue is
caused not by lack of training but by enough training to appreciate
the limitations of math expressions.

>
> > > ....
>
> > > > Mind you, many people disagree with me on this approach and call it
> > > > dumbing down.
>
> > > Me among them. Most, if not all, of the semantics wars on comp.dsp
> > > are based in this general inability to comprehend or discuss
> > > abstract concepts.
>
> > Yes, I'd say in fact that MOST people disagree with me. Except for the
> > students. :-) And the people who pay me to teach them. :-)
>
> Maybe you should have a word with the people who pay your students
> to work for them, after they leave you...

:-)

The people who pay me to teach their engineers are also the people who
pay those engineers to work for them. And the assessment alway
includes checking as to the practical value of what I taught in their
work after the courses, which (even though I am modest) is
excellent. :-)

>
> Rune- Hide quoted text -
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On 4 Feb, 10:04, Chris Bore <chris.b...@gmail.com> wrote:
> On Feb 3, 6:37&#4294967295;pm, Rune Allnor <all...@tele.ntnu.no> wrote:

> > I hit the wall when people insist on 'physical' or 'intuitive'
> > explanations for the maths. This is caused solely by lack of
> > training, and is *the* main obstacle that prevents DSP from
> > progressing forward and not un around in circles as it is
> > tending to, these days.
>
> Well, here we will have to agree to differ. I require the math to
> correspond to a practical model, for that model to be made explicit in
> ways that are not reliant simply on the math itself, and for the model
> to be tested against reality. But I do acknowledge that yours is by
> far the majority opinion.

It might be the major *opinion* but unfortunately, yours is the
most popular *approach* in actual work.

Once upon a time I came up with an abstract model for an experiemntal
scenario, that by far outperformed the standard approaches. But
because
people worked according to your philosophy, they had no way to
comprehende neither what I had done or the impact of the solution.

> Also, I don't think this is caused by lack of training. I
> misunderestimated myself when I said I was too dumb to do the math. I
> have a PhD in DSP and 30 years experience working in the field, both
> mathematically and practically. What I should have said is, that
> through deepening my understanding of the maths and studying the
> processes by which people learn in ways that enable them to apply
> their knowledge, I have become convinced that it is essential to
> complement the math with models and visualizations and that the math
> on its own is insufficient to practical application.

If I read your statement literally, I might agree with you.
However, I get the impresion that we are not talking about
"complementing" maths training, but "replacing" mats training
with infortainment.

> So the issue is
> caused not by lack of training but by enough training to appreciate
> the limitations of math expressions.

Somebody properly trained in maths would see those limitations
anyway. The reason why the mathemathics is so pedantically
formulated, is to make sure everybody understands exactly
what situations are covered, and which are not. The obvious
example within DSP is "Linear Time Invariant" systems.
The reason the texts mention these, is that whenever that
frame is exceeded (the system is  either Nonlinear or Time
Varying) the theory no longer applies.

If people have gone through engineering school and not have
seen that simple principle, the problem is their basic math
training. The solution is to point this out, not to give
in to pandering.

> > > Yes, I'd say in fact that MOST people disagree with me. Except for the
> > > students. :-) And the people who pay me to teach them. :-)
>
> > Maybe you should have a word with the people who pay your students
> > to work for them, after they leave you...
>
> :-)
>
> The people who pay me to teach their engineers are also the people who
> pay those engineers to work for them. And the assessment alway
> includes checking as to the practical value of what I taught in their
> work after the courses, which (even though I am modest) is
> excellent. :-)

Again, as far as I am concerned, giving in to pandering
is the root cause to competence rot.

Rune