Re: data and function plot causing double assignment

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

On Tuesday, October 04, 2011 08:43:02 am pl...@pi... wrote:
> On 10/04/11 17:28, Ethan Merritt wrote:
> > On Tuesday, 04 October 2011, pl...@pi... wrote:
> >> Hi,
> >>
> >> I have found what appears to be a defect in variable assignments in plot.
> >>
> >> gauss0(x)=a0*exp(-(x-pk0)**2/b0)+c0
> >> a1=a0;b1=b0;c1=c0;pk0=-141;
> >> add_one(x)=area0=1;
> >
> > This defines the function add_one(x)
> > to be  add_one(x) =   value of (area0=1)
> >                    = 1
> > So add_one(x) = 1 for all x
> 
> Exactly, so why is area still 0 after having been assigned the value 1 
> about 512 times?!

Ah. I thought you were asking about the behaviour of add_one(),
since its name implies that it performs an addition but in fact it
is defined to always equal 1.  I wondered if you didn't simply have
a typo for   "add_one_x = area0 +1".  
Anyhow...

> I reiterate that if I remove the function plot I do get areas=1 after 
> plotting. This indicates that plot is re-executing area0=0 after the 
> second data plot and before plotting the function.

I don't say this is good/bad, expected/unexpected, bug/feature, or simply
confusing, but this is the way it has always worked.  Each plot command
is evaluated once to detect functions, read in data, and determine plot
ranges; then it is evaluated again to fill in function values over the
now-determined range; then it is plotted.   If there are no functions then
the second of those three operations is skipped.

See also
  https://sourceforge.net/tracker/index.php?func=detail&aid=2907028&group_id=2055&atid=102055

	Ethan

> /Peter.
> 
> 
> > Any later changes to the value of area0 are not relevant.
> >
> > 	Ethan
> >
> >> plot  area0=0\
> >> , datafile using 1:(add_one($2)) w l\
> >> , datafile using 1:(($2)) w l\
> >> , gauss0(x) tit 'fitted peak0'\
> >>
> >> print "area0=",area0;
> >>
> >> I was expecting this to do the assignment area0=0 once and once only
> >> before any of the lines were plotted.
> >>
> >> It is only assigned once for the datafile plots but adding the function
> >> plot causes this snippet to print a value of zero , not one.
> >>
> >> I am inferring that using a mix of data and function plots is causing
> >> the initial assignment to be done twice.  Bug or feature?
> >>
> >> best regards, Peter.
> >>
> >> ------------------------------------------------------------------------------
> >> All the data continuously generated in your IT infrastructure contains a
> >> definitive record of customers, application performance, security
> >> threats, fraudulent activity and more. Splunk takes this data and makes
> >> sense of it. Business sense. IT sense. Common sense.
> >> http://p.sf.net/sfu/splunk-d2dcopy1
> >> _______________________________________________
> >> gnuplot-beta mailing list
> >> gnu...@li...
> >> https://lists.sourceforge.net/lists/listinfo/gnuplot-beta
> >>
> >
> >
> 
> 

-- 
Ethan A Merritt
Biomolecular Structure Center,  K-428 Health Sciences Bldg
University of Washington, Seattle 98195-7742