Re: Quick refresh [was: q for quit in plot windows]

[Ethan A M. <merritt@u.washington.edu>]

On Sunday 01 July 2007 16:41, Daniel J Sebald wrote:
> The following is confusing to me:
> 
> " The `volatile` keyword indicates that the contents of the data file
> may be different if the file is re-read.  This tells the program to
> use `refresh` rather than `replot` commands whenever possible.
> 
> I assume "tells the program" means "tells gnuplot".  But beyond that, the 
interpretation of this is more left to the user.  OK, "volatile" is clear.  
But for one user it may be desired that the volatile files be reread with 
every new "replot", for another user it may be desired that the volatile 
files not be reread.

Exactly. That's why they get a choice of whether to use the keyword
or not.  If you know the data may change, but you want to zoom and
play aroung with the the existing plot without reading in new data,
then you plot it with "volatile".  This tells gnuplot to keep using
the old data rather than reading in new data.

If you want to update the display with the newest available data every
time you hit the 'e' key, then you *don't* flag it volatile.  Hmmm,
yes I see that could be a bit confusing.  I'll ponder a better way
to describe it.

> In other words "volatile" is an accurate word, but implication is 
somewhat ambiguous. 

Feel free to suggest better wording, or even a different keyword.
The basic point is to provide a way to say "reread every time"
vs. "reread only when there's no other option".

> The other thing I don't like is the "whenever possible".  I've been 
trying to make the point that unless there is precise behavior for this 
feature the "whenever possible" is going to make the user or programmer 
give up in futility because he or she won't know when datafiles are 
actually reread.  "Not when log/unlog via mouse or set", "not when there 
are splines", "not for this condition", etc.  

"The perfect is the enemy of the good".  For the last 20 years
gnuplot has not allowed you to zoom volatile data.
Mostly it's been a minor annoyance.  Now there's a reason to support
it, since Octave sends data in-line.  But you are taking the extreme
position that a patch to fix this is no good unless it also re-works
log/unlog  axis rescaling. I just don't get it.

I'm perfectly happy to see the axis scaling cleaned up.
But it's an orthogonal issue.  Besides which, in all the years that
I've used gnuplot (less then 20 but more than 10 :-) I've never 
wanted to toggle log scale with a hot key.  Is this really so 
important to you?

> I'd say drop the "volatile" keyword.  Then two methods are acceptable.
> One, there are two commands "replot/refresh" in which "replot" *always* 
> rereads files and "refresh" *always* retrieves the data from memory.  

That is exactly what I implemented.  If you have found a case in 
which it doesn't act this way, please report it as a bug.

The "volatile" keyword does not affect this.

Perhaps my documentation and description is inadequate, since you seem
to misunderstand what the patch actually does.  I welcome your
help in improving the documentation, but I do not agree with you that
the log/unlog business is particularly relevant.  It's a footnote at
best: "Please note that the 'l' and 'L' hotkeys are disabled if the
plot contains in-line or volatile data".


-- 
Ethan A Merritt