gnuplot-info — For questions and discussion about gnuplot

[Gnuplot-info] Re: perl and gnuplot

[Gary P. <web...@ar...>]

Hans-Bernhard Broeker <broeker <at> physik.rwth-aachen.de> writes:
> Whatever the problem is, it's quite clearly in your Perl script.  You'll 
> have to debug it outside the web server context, or at least export the 
> actual commands it will send to gnuplot, in the problematic cases, 
> before we can even begin to look at this from the gnuplot perspective.

You're right. The problem is with perl, not gnuplot.  I tested a much simpler
version of the script that didn't involve a web form; it works fine. I'll direct
my question to a perl list.

Thanks for the reply.

BTW, I did find a way around the problem by writing the gnuplot commands to a
file and then having gnuplot retrieve the commands from the file in batch mode.

-- 
G Parker

"I hated life and was constantly on the verge of suicide, from which, however, I
was restrained by the desire to know more mathematics."
Bertrand Russell, The Conquest of Happiness (1930)

Re: [Gnuplot-info] Animation of a Triangular Mesh

[Hans-Bernhard B. <br...@ph...>]

Michael Kipper wrote:

> The intention is to use gnuplot to create an animated GIF of the mesh as it
> steps through time. Hopefully, gnuplot will recognize when a triangle in
> the foreground blocks one in the back, so I don't end up with a screen full
> of points.

Not without some hand-holding from your side.  gnuplot doesn't specially 
support triangles --- it expects surfaces to be parametric ones, even if
they come in a datafile.  To that end, it wants surfaces to have "grid 
structure", i.e. they should come as <n> sequences of <m> points, so 
gnuplot can construct a surface mesh of regular rectangular topology.

The only way to represent single triangles in this approach is as 
quadrangles with one zero-length edge.

Generally, I'm not convinced gnuplot is the right tool for this job. 
It's not designed to be a generic 3D vector graphic rendering engine. 
Other tools, like Blender or PovRay, may be better fits for the job.

Re: [Gnuplot-info] perl and gnuplot

[Hans-Bernhard B. <br...@ph...>]

Gary Parker wrote:
> I am attempting to write a perl script to allow users to plot functions using
> gnuplot through a web page.  It seems to work fine unless the function has any
> additions in it. For example, "x+1" plots as just "x" and "x**2+x" won't plot at
> all, in fact nothing with "+x" will plot.  

Whatever the problem is, it's quite clearly in your Perl script.  You'll 
have to debug it outside the web server context, or at least export the 
actual commands it will send to gnuplot, in the problematic cases, 
before we can even begin to look at this from the gnuplot perspective.

[Gnuplot-info] Re: Illegal

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[Gnuplot-info] perl and gnuplot

[Gary P. <web...@ar...>]

I am attempting to write a perl script to allow users to plot functions using
gnuplot through a web page.  It seems to work fine unless the function has any
additions in it. For example, "x+1" plots as just "x" and "x**2+x" won't plot at
all, in fact nothing with "+x" will plot.  

The apache error log has not been helpful to me.  I can post it if anyone thinks
it will help here.

I have tried running gnuplot in both batch and interactive modes.

A version of the script is availalbe at 
http://arithmometer.org/gnuplot/gnuplot_1.pl

Any suggestions would be greatly appreciated.

Gary Parker
Cayuse, OR

[Gnuplot-info] Animation of a Triangular Mesh

[Michael K. <mk...@ro...>]

Hello,

I'm new to gnuplot, as I've decided to go the open-source route, instead of
the Matlab route. So I figured I would ask the expert users how to go about
accomplishing my goal, rather than inventing myself the solution.
I have written some software to solve a problem, that creates a Delaunay
triangulated mesh of points in 3-dimensions, at specified intervals.
The intention is to use gnuplot to create an animated GIF of the mesh as it
steps through time. Hopefully, gnuplot will recognize when a triangle in
the foreground blocks one in the back, so I don't end up with a screen full
of points.
Having written the software myself, I can output the data however I like,
but cannot really figure out an efficient way to convey my data to gnuplot
to accomplish the goal.

Is there a "good" way to do this, or a tutorial somewhere I can read?

Thanks for your help and info,

Michael

[Gnuplot-info] (no subject)

[<na...@gm...>]

การอยู่ร่วมกับคนพาลมีแต่ทุกข์ เหมือนอยู่กับศัตรู

Re: [Gnuplot-info] Reading formula constants from datafile

[Hans-Bernhard B. <br...@ph...>]

Smyth, Steve wrote:

> Is it possible to read in formula constants form a datafile.  I have
> numerous functions that I would like to plot on the same figure.  All
> of the functions have the same form, but slightly different
> constants.  For simplicity, say the function is f(x)=a*x.  Can "a" be
> read in from a datafile and then f(x) plotted?

Reading one 'a' from a file, then making a plot if it, is trivial: just 
make the file read

	a = 1

then

	load 'file'
	plot f(x)

For more complex cases, e.g. involving a single plot, multiple different 
values of 'a', but only one defined function f, this won't work --- it 
would require the 'plot' command to run two nested loops, one over the 
table of values for 'a', the other over 'x'.   gnuplot doesn't do that.

Re: [Gnuplot-info] flip plot vertically

[Alessandro S. <asa...@ju...>]

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

i really beg your pardon... usually i always refrain from asking silly
questions before having thought lengthly enough... but i was too much
in a hurry

what a shame... I've found out that

set set yrange [1:1e-5]
set log y

does the trick

thank you :)

Alessandro Salvatori wrote:

> Hi,
> sorry to bother, but i have very little time and google is not
> helping much :(
>
> is there a way to flip the y-axis (have values increase from the top
> to the bottom)?
> it's not just a matter of giving labels to tics and putting a minus in
> front of the second column of data, as my plot is in logscale...
>
> thank you very much indeed!
> Alessandro Salvatori


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[Gnuplot-info] flip plot vertically

[Alessandro S. <asa...@ju...>]

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

Hi,
  sorry to bother, but i have very little time and google is not
helping much :(

is there a way to flip the y-axis (have values increase from the top
to the bottom)?
it's not just a matter of giving labels to tics and putting a minus in
front of the second column of data, as my plot is in logscale...

thank you very much indeed!
Alessandro Salvatori
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Comment: Using GnuPG with Thunderbird - http://enigmail.mozdev.org

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[Gnuplot-info] Reading formula constants from datafile

[Smyth, S. <Ste...@nr...>]

Is it possible to read in formula constants form a datafile.  I have numerous functions that I would like to plot on the same figure.  All of the functions have the same form, but slightly different constants.  For simplicity, say the function is f(x)=a*x.  Can "a" be read in from a datafile and then f(x) plotted?

 

Any guidance would be appreciated.

 

Thanks

 

Steve Smyth

 

 

 

[Gnuplot-info] Re: wrong simple linear fit

[Eckard S. <sp...@hy...>]

Dear Hans-Bernhard,

thank you very much for the explanation. In all interactive gnuplot sessions,
such problems can be recognized and avoided. But for 'batch' sessions this
strategy is too restrictive. However, gnuplot is a wonderful tool.

<a href=http://hydra.nat.uni-magdeburg.de/praktikum/>Here</a> is the "little
helper".

Best regards,
-Eckard

Re: [Gnuplot-info] wrong simple linear fit

[Hans-Bernhard B. <br...@ph...>]

Eckard Specht wrote:

> gnuplot comes up with a totally wrong regression line (i.e. a negative slope).
> If one scratches one data pair from list, the result is correct.
> 
> I have read in 'help fit' that this misfit can occur if the magnitudes of both
> parameters a, b differ too much. This may be the case here.

Not if the parameters are this different, the default startup values of 
1.0 three orders of magnitude from the goal, and, which is the worst 
problem here, and the actual value for one of the fitted parameters (b) 
is zero, which makes it uncontrollable by the fit:

    fit m*x 'lreg3.dat' via m

gives a very nice fit already:

After 5 iterations the fit converged.
final sum of squares of residuals : 2.48482e-007
rel. change during last iteration : -6.69962e-012

degrees of freedom (ndf) : 5
rms of residuals      (stdfit) = sqrt(WSSR/ndf)      : 0.000222927
variance of residuals (reduced chisquare) = WSSR/ndf : 4.96965e-008

Final set of parameters            Asymptotic Standard Error
=======================            ==========================

m               = 6.62853e-007     +/- 1.134e-010   (0.01711%)

So the actual result is b=0, which means the magnitude ratio of the 
parameters is *infinite*.  That will indeed throw off the fit.

> But a simple linear fit should always work. Or not?

Not.  It has a higher chance of success, but no guarantee.

> Is it true that the Marquardt-Levenberg algorithm is used for all fits?

Yes.

> Must I provide 'good' starting values for a, b to get a correct result? 

That, and a sensible model.  Models in which parameters would fit zero
won't work.

[Gnuplot-info] wrong simple linear fit

[Eckard S. <sp...@hy...>]

Hi@all,

I'm not sure if my fit problem with gnuplot is an old hat. I have built a site
that helps students to get results from physical experiments by the help of
gnuplot. All is well but for a simple linear fit I get wrong parameters.

My data are:
6.03e5  0.4
6.79e5  0.45
7.54e5  0.5
8.30e5  0.55
9.05e5  0.6
9.81e5  0.65
which are stored in a file 'lreg3.dat'.

My gnuplot commands are:
f(x) = a*x+b
fit f(x) 'lreg3.dat' via a,b
plot f(x), 'lreg3.dat'

gnuplot comes up with a totally wrong regression line (i.e. a negative slope).
If one scratches one data pair from list, the result is correct.

I have read in 'help fit' that this misfit can occur if the magnitudes of both
parameters a, b differ too much. This may be the case here. But a simple linear
fit should always work. Or not?

Is it true that the Marquardt-Levenberg algorithm is used for all fits?

Must I provide 'good' starting values for a, b to get a correct result? This
would be very inconvenient here.

Thank you very much for your help/comments.

Regards,
-Eckard

Re: [Gnuplot-info] Using gnuplot from inside data space

[Hans-Bernhard B. <br...@ph...>]

Christopher John Muller wrote:
> Is there an easy way that the viewing point and general direction can be
> specified, 

Not with any existing version.  There's a patch that enables point 
perspective, IIRC, but guess even that won't discard data behind the viewer.

[Gnuplot-info] Using gnuplot from inside data space

[Christopher J. M. <c.j...@dl...>]

Hi to the team.

Is there an easy way that the viewing point and general direction can be
specified, so that an inside to outside view of a data set may be
obtained. I am thinking probably slightly misguided, that 'gnuplot'
could realise a greater 3D potential.

See attached plot image. 'InsideAtom.gif"

Regards Chris. Muller
c.j...@dl...

Re: [Gnuplot-info] Splot and plot at the same time

[Hans-Bernhard B. <br...@ph...>]

Fernando Sales wrote:
> Hello. I wanted to know whether there's a way to plot a contour plot with splot
> and some few trajectories with 'plot' at the same time, to see them both toge-
> ther in the same picture. 

No.  But you can save the contour lines to a separate datafile (see 
'help contour'), and 'plot' that along with the other one.  Or you can
'splot' the trajectories along with the contoured surface.  That may end 
up a bit confusing, though.

[Gnuplot-info] Splot and plot at the same time

[Fernando S. <fs...@au...>]

Hello. I wanted to know whether there's a way to plot a contour plot with splot
and some few trajectories with 'plot' at the same time, to see them both toge-
ther in the same picture. I'm using version 4.0 for windows. Thank you for your
help.

Fernando

Re: [Gnuplot-info] help: no graph terminal pops up

[Dieter J. <die...@t-...>]

Hi Damian,
Mr. Broeker is 100% right - and some additional information is neccessary t=
o=20
help you further out:
=2D what is your OS? I assume linux?!?
=2D what distribution do you use? Debian, Suse, Fedora ...
=2D do you have root access to the machine?
The procedure how to install the devel-packages differs between the=20
distributions. I can help with debian and SuSE, might not be too difficult=
=20
for other distributions, but I have to know what your system is!
Take care



Dieter

Am Dienstag, 14. Juni 2005 15:52 schrieb Damian A Scherlis Perel:
>  Dear Hans,
>
> > Your installation misses the X11 development packages (headers,
****

=2D-=20
=2D----------------------------------------------------------

                               |
                                \
                 /\_/\           |
                | ~x~ |/-----\   /
                 \   /-       \_/
  ^^__   _        /  _  ____   /
 <=B0=B0__ \- \_/     |  |/    |  |
  ||  ||         _| _|    _| _|

if you really want to see the pictures above - use some font
with constant spacing like courier! :-)
=2D----------------------------------------------------------

Re: [Gnuplot-info] help: no graph terminal pops up

[Damian A S. P. <da...@MI...>]

 Dear Hans,

> Your installation misses the X11 development packages (headers,
> libraries, ...).  Install them, rerun the gnuplot build starting at
> 'configure'.
>
 I understand that that is the problem, but still I can't
 figure out how to install the missing packages.
 I have tried './configure --with-x' to no avail.
 Any hint will be very much appreciated.
 Thank you!
              damian

Re: [Gnuplot-info] help: no graph terminal pops up

[Hans-Bernhard B. <br...@ph...>]

Damian A Scherlis Perel wrote:
>  I have installed gnuplot-4.0.0 following the default
>  procedure (./configure, make, make install) in a Red-Hat
>  Enterprise environment. The installation ends without
>  errors, but when I execute the program under X-windows I get
>  the message "Terminal type set to 'unknown'" preceding
>  the prompt, and no graphics window pops up when I
>  enter "plot ..." (i.e. plot sin(x)) at the command line.

Your installation misses the X11 development packages (headers, 
libraries, ...).  Install them, rerun the gnuplot build starting at 
'configure'.

Re: [Gnuplot-info] help: no graph terminal pops up

[Damian A S. P. <da...@MI...>]

 Juanjo,

 thanks a lot for your answer.

> Try this:
>
> gnuplot> set termina x11
> Terminal type set to 'x11'
> Options are '0'
> gnuplot> plot sin(x)
>

 However, it doesn't work either. If I try that, I get this message:
unknown or ambiguous terminal type; type just 'set terminal' for a list

 Gracias,
           damian

Re: [Gnuplot-info] help: no graph terminal pops up

[Juanjo C. <jj...@gn...>]

Damian A Scherlis Perel wrote:
>  Dear all,
> 
>  I have installed gnuplot-4.0.0 following the default
>  procedure (./configure, make, make install) in a Red-Hat
>  Enterprise environment. The installation ends without
>  errors, but when I execute the program under X-windows I get
>  the message "Terminal type set to 'unknown'" preceding
>  the prompt, and no graphics window pops up when I
>  enter "plot ..." (i.e. plot sin(x)) at the command line.

Try this:

gnuplot> set termina x11
Terminal type set to 'x11'
Options are '0'
gnuplot> plot sin(x)

I'm using gnuplot 4.0 patchlevel 0 on Debian, let me know if it worked.

Bye!

Juanjo

PS: list-admin, when I click on 'Reply' at Thunderbird I compose a 
message por the original message writter (here Damian), I think it would 
be betther if when you click on 'Reply' the default value be 
gnu...@li... (I hope I could express the idea I 
wanted in english, sorry)

[Gnuplot-info] help: no graph terminal pops up

[Damian A S. P. <da...@MI...>]

 Dear all,

 I have installed gnuplot-4.0.0 following the default
 procedure (./configure, make, make install) in a Red-Hat
 Enterprise environment. The installation ends without
 errors, but when I execute the program under X-windows I get
 the message "Terminal type set to 'unknown'" preceding
 the prompt, and no graphics window pops up when I
 enter "plot ..." (i.e. plot sin(x)) at the command line.

 I see a bunch of options if I type "set terminal", but
 no X11 or equivalent.

 I have also tried ./configure --with-x, but still the same.
 Any help will be greatly appreciated.
 Thanks!
                 damian

 ------------------------
 Damian Scherlis
 Department of Materials Science & Engineering
 Massachusetts Institute of Technology
 da...@mi...
 617 253 6026

[Gnuplot-info] =?us-ascii?Q?gnuplot=204=2E0=2E0?=

[<re...@se...>]

Hi,

I'm using Gnuplot in my project. I'd like to use functions from Gnuplot 4.0.0 (e.g. pm3d, interactions with mouse and keyboard...). I downloaded Gnuplot on the www.gnuplot.info and other serveres. When I instaled it and lunched it, it said Gnuplot 3.7 patchlevel 3. Please, do you know where it's possibile to download indeed Gnuplot 4.0.0 or higher for Linux Mandrake ?

Thank you very much. Good luck in development of Gnuplot.


Libor Simek
____________________________________________________________
http://www.listicka.cz