From: Nick Finnigan on
Robin Stevens wrote:
> In cam.transport Nick Finnigan <nix(a)genie.co.uk> wrote:
>> Patrick Gosling wrote:
>>> Nick Finnigan <nix(a)genie.co.uk> wrote:

>>> Do you suppose that an investigation into the dependency of a mechanical
>>> system on the current barometric pressure will be improved by an
>>> insistence on not having an origin somewhere near 1000 mbar?
>> Yes.
>
> How, precisely?

It will not imply that there is anything special about a bar, nor that
there is anything negative about being below a bar.
From: Robin Stevens on
In cam.transport Nick Finnigan <nix(a)genie.co.uk> wrote:
> Robin Stevens wrote:
> > In cam.transport Nick Finnigan <nix(a)genie.co.uk> wrote:
> >> Patrick Gosling wrote:
> >>> Nick Finnigan <nix(a)genie.co.uk> wrote:
> >>> Do you suppose that an investigation into the dependency of a mechanical
> >>> system on the current barometric pressure will be improved by an
> >>> insistence on not having an origin somewhere near 1000 mbar?
> >> Yes.
> > How, precisely?
> It will not imply that there is anything special about a bar, nor that
> there is anything negative about being below a bar.

And this is far more important than clearly showing the variations your
audience actually care about? Particularly when it's an audience of
trained scientists/engineers rather than a rabble of tabloid readers?

How about, rather than choosing a totally arbitrary origin at say
950mbar, you choose mean atmospheric pressure at sea level?

--
Robin Stevens <rejs(a)cynic.org.uk>
---- http://www.cynic.org.uk/ ----
From: Nick Finnigan on
Robin Stevens wrote:
> In cam.transport Nick Finnigan <nix(a)genie.co.uk> wrote:
>> Robin Stevens wrote:
>>> In cam.transport Nick Finnigan <nix(a)genie.co.uk> wrote:
>>>> Patrick Gosling wrote:
>>>>> Nick Finnigan <nix(a)genie.co.uk> wrote:
>>>>> Do you suppose that an investigation into the dependency of a mechanical
>>>>> system on the current barometric pressure will be improved by an
>>>>> insistence on not having an origin somewhere near 1000 mbar?
>>>> Yes.
>>> How, precisely?

>> It will not imply that there is anything special about a bar, nor that
>> there is anything negative about being below a bar.
>
> And this is far more important than clearly showing the variations your
> audience actually care about? Particularly when it's an audience of
> trained scientists/engineers rather than a rabble of tabloid readers?

Including aeronautical engineers?

> How about, rather than choosing a totally arbitrary origin at say
> 950mbar, you choose mean atmospheric pressure at sea level?

How about choosing the minimum possible pressure for the system?
From: Albert T Cone on
Nick Finnigan wrote:
> Albert T Cone wrote:
>>
>> If we are talking about a scientific publication, as I understood us
>> to be, then the proper way to present the data is that which lets it
>> be read most accurately; in this case with axes offset. Anyone of a
>> scientific grounding *should* read the axes carefully.
>
> It is read most accurately with the Origin at zero.
No. Not for accepted interpretations of the word 'accurately'.

> If the variation
> can not be seen with that presentation, it is not important.

What a bizarre and rather stupid claim.
Plotting the variation in daytime temperature on an absolute scale,
using an origin of zero, I suggest that you would not be able to read
the variation, however that variation is very significant, wouldn't you say?

Similarly, a global temperature rise of 1K would be hugely significant,
but virtually invisible on a plot scaled to include the range 0-300K.

If the bearings in the wheels of your bike or car varied in radius by
1%, the bearing would work extremely poorly and fail quickly, but the
manufacturer wouldn't be able to see that variation on his scatter
plots, so it couldn't be important, right?
From: J. Chisholm on
Nick Finnigan wrote:
> Albert T Cone wrote:
>>
>> If we are talking about a scientific publication, as I understood us
>> to be, then the proper way to present the data is that which lets it
>> be read most accurately; in this case with axes offset. Anyone of a
>> scientific grounding *should* read the axes carefully.
>
> It is read most accurately with the Origin at zero. If the variation
> can not be seen with that presentation, it is not important.

Rubbish

If I were making a study of the variability of a machine loading 1 tonne
bags with fertilizer, plotting the results about zero would be madness.

I remember an early computer program to determine standard deviation. It
worked fine for numbers about zero, but in the case above it would give
errors. The program summed the squares (about zero) which resulted in
VERY large numbers (and hence errors). The correct way with large
numbers and small variance is to have a 'moving' sum of squares about
the 'moving' average. This was a mainframe package pre 1970

Jim