gnuplot-beta

Multiplot fails in postscript mode

[Lutz M. <ma...@uc...>]

I noticed the following behavior in gnuplot 4.0 under linux: In a new gnuplot 
session, copy&paste the following command:

set term post; set outp 'test.ps'; set multiplot; set size 1,0.5; set origin 
0,0.5; splot x**2+y**2; set origin 0,0; splot x**2+y**2; unset multiplot; set 
outp

This will create a postscript file "test.ps", which contains two plots as 
expected. Now execute this line again. The resulting postscript file contains 
only one plot. Is this the expected behavior?

  Lutz

Re: Multiplot fails in postscript mode

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

On Friday 04 June 2004 11:45 am, Lutz Maibaum wrote:
> I noticed the following behavior in gnuplot 4.0 under linux: In a new
> gnuplot session, copy&paste the following command:
>
> set term post; set outp 'test.ps'; set multiplot; set size 1,0.5; set
> origin 0,0.5; splot x**2+y**2; set origin 0,0; splot x**2+y**2; unset
> multiplot; set outp
>
> This will create a postscript file "test.ps", which contains two plots
> as expected. Now execute this line again. The resulting postscript file
> contains only one plot. Is this the expected behavior?

Yes, I believe it is the expected behaviour.

At the time of your first 'set output' the size was set to 1,1
so you created a full-size plot canvas.  That is, the bounding
box encompassed the entire page.

Later you set the size to 1,0.5

At the time of your second 'set output' the size was still
set to 1,0.5  and so you created only a half-size plot canvas.

If you look at the second postscript file you will see that
both of your plots are there; it's just that one of them is
drawn onto the half of the page that is outside the bounding
box.


-- 
Ethan A Merritt       merritt@u.washington.edu
Biomolecular Structure Center
Mailstop 357742
University of Washington, Seattle, WA 98195

Re: Multiplot fails in postscript mode

[Lutz M. <ma...@uc...>]

Thank you very much for your explanations, Ethan and Hans. It seems that the 
"size" setting has very different effects when evaluated by "set multiplot" 
and by the plot command. It would be nice if this dual meaning could be 
mentioned in the help entry of "set size".

  Lutz

Re: Multiplot fails in postscript mode

[Daniel J S. <dan...@ie...>]

Lutz Maibaum wrote:

>Thank you very much for your explanations, Ethan and Hans. It seems that the 
>"size" setting has very different effects when evaluated by "set multiplot" 
>and by the plot command. It would be nice if this dual meaning could be 
>mentioned in the help entry of "set size".
>
>  Lutz
>  
>

Since this topic has come up...

I've thought for a while that a tutorial of plot layout would be a nice 
thing.  Something that illustrates the view, how size behaves, how 
coordinates behave, how labels get placed, etc.  But I'll put that in 
the "longterm" bin, i.e., maybe if ever some free time.

Anyway, the immediate issue is the difficulty in which to get multiplots 
laid out in anything but the default manner.  I'll give an example to 
illustrate the frustration.  I recently created a plot for which I 
wanted the following

1)  6 x 1 configuration, i.e., six plots stacked vertically.
2)  Tic marks outside the borders because otherwise they would interfere 
with what is in the plot.
3)  All six plots share the same x-axis.  Hence, to free up space, I 
wanted only the bottom plot to have units and tic marks.
4)  I wanted just one y-axis label, centered somewhere between the third 
and fourth plots.

OK, it is #3 that really poses the problem.  Here is a string of 
commands that basically captures the ideas I used to lay out the multiplot:

set multiplot
unset key
unset xlabel
unset xtics
set tics out
set size 0.95,0.3
set origin 0.05,0.7
plot sin(x)
set origin 0.05,0.4
plot sin(x+0.78540)
set origin 0.05,0.0
set xtics nomirror
set xlabel "time (s)"
set label 1 "amplitude" at screen 0.03,0.53 center rotate front
plot sin(x+1.5708)
unset multiplot

However, I had to do some tweaking of dimensions, but I left that undone 
here for illustration.

If you enter these commands, you'll see what the main issue is.  That 
bottom plot is different in terms of label configuration.  The way 
gnuplot works, when one says "size" it refers to the overall dimension 
of the plot *including* labels.  Hence, that bottom plot comes out 
smaller than all the rest.  No problem, you say.  Just issue a different 
size for the bottom plot, maybe

set size 0.95,0.4

Sure, but try it.  The trial an error process soon got the best of me. 
 You want the borders to be the same dimension (adjusting "size"), and 
you want the spacing between plots to be just right (adjusting 
"origin"), and you want the xlabel to not go too far off the view 
(adjusting "size" and "origin" again).  One could remove the xlabel and 
instead put another "label 2", but there is still the units and tics.

OK, if you've looked at the result of the commands above, you can 
imagine tweaking things with relative ease to get it to look right.  But 
now try getting things as you want using the "pslatex" terminal.  This 
isn't WYSIWYG, so it is the whole process over again; and this time one 
has to generate pslatex, compile tex, generate pslatex, compile tex, 
etc.  And you sort of need the X11 layout as a guide.  If you compare 
the layout parameters for proper pslatex layout, the X11 view looks like 
a mish-mash of overlapping plots and labels.

I eventually got what I wanted, and it looks great.  But it sure took 
enough time.

Bottom line: can anyone think of a syntax and scheme that would allow 
better control for this?  For example, just as "coordinates" have a 
"system" reference (i.e., `first`, `second`, `graph` or `screen`) could 
it be possible for "size" to reference 'border' or 'overall' or 
something like that.  The idea would be for some way to have the borders 
of your plots be exactly the size you specify.  I don't think I'm 
overlooking anything that would have made life simple here.  Thoughts?

Dan

Hold On... (Re: Multiplot fails in postscript mode)

[Daniel J S. <dan...@ie...>]

Daniel J Sebald wrote:

> Bottom line: can anyone think of a syntax and scheme that would allow 
> better control for this?  For example, just as "coordinates" have a 
> "system" reference (i.e., `first`, `second`, `graph` or `screen`) 
> could it be possible for "size" to reference 'border' or 'overall' or 
> something like that.  The idea would be for some way to have the 
> borders of your plots be exactly the size you specify.  I don't think 
> I'm overlooking anything that would have made life simple here.  
> Thoughts? 


Hold on.  Maybe I did overlook an alternative.  One can solve the 
unequal borders problem by creating a phantom tic/unit for the top plots 
and placing a label for the bottom xlabel.  I.e.,

set multiplot
unset key
unset xlabel
set xtics nomirror
set xtics ("" 1e100)
set tics out
set size 0.95,0.35
set origin 0.05,0.6
plot sin(x)
set origin 0.05,0.315
plot sin(x+0.78540)
set origin 0.05,0.03
set xtics autofreq
set label 1 "amplitude" at screen 0.03,0.53 center rotate front
set label 2 "time (s)" at screen 0.53,0.03 center front
plot sin(x+1.5708)
unset multiplot

I'll just mumble to myself here for a while...

Dan

Re: Multiplot fails in postscript mode

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

On Saturday 05 June 2004 09:47 am, Daniel J Sebald wrote:
>
> Anyway, the immediate issue is the difficulty in which to get multiplots
> laid out in anything but the default manner.

[snip example of stacked plots]

> Bottom line: can anyone think of a syntax and scheme that would allow
> better control for this?

I think we already have it.
	set {b|l|r}margin 0

That should line all the plots up regardless of labels or tics,
at the cost of having to explicitly position them in from the page
boundary.

One remaining issue for such stacked plots, however, is trying
to collect all of the plot labels into a single key.  I can't think of
an easy way to do that.  

Is there something else missing?

-- 
Ethan A Merritt
Department of Biochemistry & Biomolecular Structure Center
University of Washington, Seattle

Re: Multiplot fails in postscript mode

[Daniel J S. <dan...@ie...>]

Ethan A Merritt wrote:

>On Saturday 05 June 2004 09:47 am, Daniel J Sebald wrote:
>  
>
>>Anyway, the immediate issue is the difficulty in which to get multiplots
>>laid out in anything but the default manner.
>>    
>>
>
>[snip example of stacked plots]
>
>  
>
>>Bottom line: can anyone think of a syntax and scheme that would allow
>>better control for this?
>>    
>>
>
>I think we already have it.
>	set {b|l|r}margin 0
>
>That should line all the plots up regardless of labels or tics,
>at the cost of having to explicitly position them in from the page
>boundary.
>

Right...  This is the kind of thing there should be a 5 page tutorial 
for, or a demo.  Something titled "Plot Layout".

>One remaining issue for such stacked plots, however, is trying
>to collect all of the plot labels into a single key.  I can't think of
>an easy way to do that.
>

That is a problem.  But in this case it was a bunch of stacked 
histograms, i.e., no real white space within the plots.  So the key 
would cover up some information, and not really provide anything useful.

>Is there something else missing?
>

No, I think that does the trick.  Thanks Ethan.

Dan

Re: Multiplot fails in postscript mode

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

On Friday 04 June 2004 12:59 pm, Ethan Merritt wrote:
> >The resulting postscript
> > file contains only one plot. Is this the expected behavior?
>
> Yes, I believe it is the expected behaviour.

On the other hand, I think it would be reasonable for
set/unset multiplot to save and restore the plot size.
Logically it should then also save and restore the
origin.

Is that what you expected to happen? 

-- 
Ethan A Merritt       merritt@u.washington.edu
Biomolecular Structure Center
Mailstop 357742
University of Washington, Seattle, WA 98195

Re: Multiplot fails in postscript mode

[Lutz M. <ma...@uc...>]

On Friday 04 June 2004 14:18, Ethan Merritt wrote:
> On the other hand, I think it would be reasonable for
> set/unset multiplot to save and restore the plot size.
> Logically it should then also save and restore the
> origin.
>
> Is that what you expected to happen?

I'm not sure I understand your question. The way I use gnuplot, I would have 
expected the following (I will use the word "canvas" for the output medium, 
it could be an X window, or a sheet of paper. I think this is equivalent to 
the "screen" coordinate system in gnuplot):

"set multiplot": tells the plot command that the canvas shouldn't be cleared 
before the plot.

"set size xscale, yscale": tells the plot command that the whole plot should 
be scaled in x- and y-direction. "set size 1,1" means using the whole canvas.

"set origin x,y": tells the plot command to shift the plot by (x,y), where 
(0,0) is the bottom left and (1,1) is the top right corner of the canvas.

If I wanted to change the canvas size (for example, the resolution of a bitmap 
plot, or the paper size), I would expect this to be done using "set terminal 
<whatever> <canvas size>".

  Lutz

Re: Multiplot fails in postscript mode

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

On Friday 04 June 2004 04:56 pm, you wrote:

I'm not sure I can make things any clearer, but I'll try.

> The way I use gnuplot, I would have expected the following.
> "set multiplot": tells the plot command that the canvas shouldn't be
> cleared before the plot.

Not quite correct. "set multiplot" tells gnuplot that the canvas should not
be reset *after* the plot, or indeed after the next several plots leading
up to "unset multiplot".  It also tells gnuplot there are a number of other
things it should not allow while in multiplot mode (most of them pretty
obvious - like not change the terminal type).

> If I wanted to change the canvas size (for example, the resolution of a
> bitmap plot, or the paper size), I would expect this to be done using "set
> terminal <whatever> <canvas size>".

I was using "canvas" to refer to the subarea within the physical page
or window or piece of paper within which the plot lies.  The size of the
page or window or paper is a separate specification, and is unfortunately 
terminal-specific. For instance
	set term png size 600,480
	set term dumb 79 49
Perhaps even more unfortunately, there is no such option for the
PostScript terminal.  That may be the real bug here, if there is one. 

Anyhow, "set size" is independent of this, and controls how much of that
terminal size (or page size) can be written on by the next plot.

Consider:

	set term png size 600,480
	set size 0.5, 0.5
	plot sin(x)

	set term png size 300,240
	set size 1,1
	plot sin(x)

Both of these will produce a graph that occupies roughly 300x240
pixels, but the first one will be surrounded by a lot of empty space
in a large window.  The second one will be in a smaller window which
it mostly fills.

In the second plot of your example you told the postscript driver
that it could only write to half of the total paper ("set size 1,0.5"),
and so that's what it did.

-- 
Ethan A Merritt
Department of Biochemistry & Biomolecular Structure Center
University of Washington, Seattle

Re: Multiplot fails in postscript mode

[Lutz M. <ma...@uc...>]

On Friday 04 June 2004 21:54, Ethan A Merritt wrote:
> Consider:
>
> 	set term png size 600,480
> 	set size 0.5, 0.5
> 	plot sin(x)
>
> 	set term png size 300,240
> 	set size 1,1
> 	plot sin(x)
>
> Both of these will produce a graph that occupies roughly 300x240
> pixels, but the first one will be surrounded by a lot of empty space
> in a large window.  The second one will be in a smaller window which
> it mostly fills.

This is exactly the behavior I would expect: you define the size of the 
created image (i.e., the resolution) in the "set term" command, and the size 
of a graph relative to the total image size using "set size".

> In the second plot of your example you told the postscript driver
> that it could only write to half of the total paper ("set size 1,0.5"),
> and so that's what it did.

I wasn't aware that this is what the "set size" command does. I though that it 
tells gnuplot that "whatever graph you plot, do it in a way that it covers 
the whole width of the output medium, but only half its height". I didn't 
expect the "set size" command to change the size of the output medium itself, 
which I thought was always 10"x7" for the postscript terminal.

  Lutz