Re: gnuplot 5.0.1?

[<pl...@pi...>]

On 07/06/15 07:25, sfeam wrote:
> On Sunday, 07 June 2015 Tatsuro MATSUOKA <tma...@ya...> wrote:
>
>  > The gnuplot web site announces that ver. 5.0.1 is released.
>
>  >
>
>  > http://www.gnuplot.info/ReleaseNotes_5_0_1.html
>
>  >
>
>  >
>
>  > However, on the sourceforge site does not contain 5.0.1 contents.
>
>  >
>
>  > Is this mere delay of sourceforge site?
>
> Karl Ratzsch requested that we look at Bug #1594 before releasing 5.0.1
>
> There has been some discussion, so I have waited to learn if
>
> there is agreement how it should be fixed.
>
> Right now I am leaning towards restoring 4.6.6 behavior (second bracketed
>
> range applies to column 2 of input data, which makes sense, and that
>
> column is called z, which makes no sense to me but it's been like that
>
> for 5 years). I will also print a warning line to the console
>
> and to the log file stating exactly what is done, if anything, to
>
> filter input based on the range of the independent variable.
>
> The output in the log file would look like this:
>
> %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
>
> FIT: data read from 'lcdemo.dat'
>
> format = z
>
> Warning: using last bracketed range to filter input data lines
>
> based on value of the independent variable in column 2
>
> independent variable range restricted to [1.02700 : 1.05000]
>
> #datapoints = 14
>
> residuals are weighted equally (unit weight)
>
> %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
>
> If people are OK with that I will prepare a release tarball tomorrow
>
> containing that one change from today's cvs.
>
> If there is no agreement, I will prepare a release tarball that does
>
> not contain a fix for Bug #1594 but will add it to the "KNOWN ISSUES"
>
> section of the release notes.
>
> best regards,
>
> Ethan
>


If a warning is to be printed to console, I think this should be AFTER 
all the usual stream of output during fit and the fit results and stats, 
otherwise it is likely to go completely unnoticed.


  ".... independent variable in column 2....independent variable range 
restricted   "

Isn't col 2 treated as being the DEPENDANT variable?

Also explicitly stating col 2 will not be correct if 'using' clause says 
otherwise !  eg using 1:3  or 1:($3+$4)


"residuals are weighted equally (unit weight)"

This would be a good place to state explicitly that the ( correctly 
named ) independant variable : x or column 1 or whatever was specified 
in 'using' clause is assumed to have zero error unless xyerror options 
is used.


While your argument that gnuplot should just assume that users are using 
the function "responsibly"  seems sensible, the problem is that a 
worrying proportion of people even at PhD level seem blissfully unaware 
of the basic assumptions involved in LSQ fitting and thus are not act 
responsibly.

You don't need to search very far before finding someone using LSQ on a 
scatter plot between two error laden experimental variables, usually 
resulting in regression dilution and erroneously low fitted "slope". 
This is often visible obvious if one is aware of the problem but people 
have so much faith in LSQ that they never question it.

If a message is now deemed necessary due to the rather crazy changes 
made 5 years ago, this presents a good opportunity to help users be 
aware of the assumption of zero ( or negligible ) error in x  in LSQ 
fitting.

This may at least prompt them to inform themselves of the issue.

Peter.