Fwd: Patch 1757226 : probability scaling and axes

[James R. V. Z. <jr...@co...>]

Philipp -

You wrote:
> I took a look at an older patch 1757226 (probability
> scaling and axes).
> 
> I like the idea a lot, but the patch is large and a bit older. I am
> also not sure how "complete" the patch is in its current form - the
> "todo" list is a bit lengthy.
> 
> Has somebody else taken a look at it? Is James (the original
> submitter) still around to help get it in line with the current
> (4.3) devel version of gnuplot?

I am still around (though not always keeping up with my email :-).
and am still interested in probability and more general scaling and
axes.  

> Since your sourceforge email bounced...

Hmm.  Apparently they don't know about my current email address.  And
they don't recognize the username/password in my Firefox registry and
notebook.

> Are you still interested in this patch and
> would be willing to revivify it? ;-)

Certainly.  I may need CVS access renewed, depending on how my account
gets straightened out.

Ethan A Merritt writes:

> I would really like to see this implemented in the general form
> mentioned on the TODO list. That is, I want a mechanism for mapping
> an arbitrary monotonic function f(x) onto a display axis.
> Both log(x) and probability(x) could become special cases of this
> general code rather than being separate parallel code paths.

Yes, with a couple of caveats.  I expect it will take some tuning
before people are happy with log scaling in all cases.  In the mean
time, I expect we should maintain both mechanisms.  My code for
probability scaling makes use of the analytic expressions for forward
and inverse scaling, plus the known range of values (open interval
between zero and one).  Some of the underlying code handles the more
general case where only one function is supplied, and it's inverted
numerically.  I haven't tried to figure out the range automatically,
though.  We'll have to decide how much of that information we expect
from the user.

> Furthermore, this would present an excuse^H^H^Hopportunity to
> re-work how data values are stored internally.  Right now setting
> log-scaling on an axis causes the corresponding data coordinate to
> be transformed and stored as the log.  This creates great headaches
> if you want to toggle the log-scaling and redraw the plot from the
> data previously read in.  I think it would be much cleaner and more
> flexible to store the original coordinate value on input, and only
> apply the log- or other scaling during plot generation.

Yes!  One reason I didn't take my patch any further was that the "last
minute scaling" revision ought to be done first.

              - Jim Van Zandt