Re: Does "fit" really need to use the axis structures?

[Bastian M. <bma...@we...>]

Am 12.06.2013 23:29, schrieb Ethan A Merritt:
> In response to a request on the newsgroup, I've been looking into relaxing
> the limit of 5 independent parameters in "fit".
>
> So far as I can see there are 2 reasons for this limit.
>
> 1)  df_readline() limits the number of fields in a 'using' clause to
>      MAXDATACOLS, and this is currently defined as 7.
>
> 2)  the fit parameters can be range-limited in the "fit" command,
>      and these ranges are stored in the axis data structures for the
>      x, y, t, u, and v axes.
>
> (1) It is easy to change MAXDATACOLS, and I have confirmed that by
> itself this doesn't break anything.
>
> (2) is harder to relax if it really is necessary to use the axis data
> structures.  But is it really necessary?
>
> It looks to me that the only reason the axis data structures are involved
> is that routine parse_range(), which used to be macro PARSE_NAMED_RANGE,
> takes an axis index as input parameter and overwrites the
> autoscale/min/max fields in that axis structure.
> During the fit operation, these ranges are checked in the axis structure.
>
> Is there some other reason I am missing that requires access to the
> axis data structures?  Can we just provide a local array containing
> autoscale/min/max for each fit parameter and not access the axis
> structures at all?
>
> 	Ethan

I am not familiar enough with the axis structures to comment on this. 
The fitting code itself certainly does not have a restriction to the 
number of indep. variables.  Hans-Bernhard, any comments?

Support for up to five independent variables was implemented by Jim Van 
Zandt.  Interestingly, the discussion about the axis array was brought 
up already in the original discussion:
http://thread.gmane.org/gmane.comp.graphics.gnuplot.devel/8319

There was also was a proposal by SF user Hanno, where he discusses a 
patch he was working on with support for more than 2 indep. variables. 
Sadly, no code is attached.
http://sourceforge.net/p/gnuplot/feature-requests/191/

   Bastian