PyX

Hi,

> I'm trying to plot several data set using line (no symbols). However, I d=
on't=20
> know how to change the color or the dashed size for the linestyle. Could =
some=20
> body help?

at <http://pyx.sourceforge.net/documentation.html> you will find an FAQ.
Question 3.3.3 "How do I choose the line style?" should address your
problem. You might also want to take a look at the graph examples at
<http://pyx.sourceforge.net/examples/graphs/index.html>. change.py
demonstrates for example how you can change styles in an automatic way.
For the dash lengths, appendix D of the manual may be useful.

Best regards,
Gert

--=20
 Gert-Ludwig Ingold        email: Gert.Ingold@...
 Institut f=FCr Physik       Phone: +49-821-598-3234
 Universit=E4t Augsburg      Fax  : +49-821-598-3222
 D-86135 Augsburg          WWW  : http://www.physik.uni-augsburg.de/theo1/ingold
 Germany                   PGP  : 86FF5A93, key available from homepage

Hi,

On 12.01.05, Toan T Nguyen wrote:
> I'm new to PyX

Welcome!

> and could not find the relevant information from the documents.  
> I'm trying to plot several data set using line (no symbols). However, I don't 
> know how to change the color or the dashed size for the linestyle. Could some 
> body help?

The graph example change.py is what you're looking for. A slightly
modified version for a short discussion here:

    from pyx import *

    g = graph.graphxy(width=10, x=graph.axis.linear(min=0, max=2))
    g.plot([graph.data.function("y=x**i", context={"i": i})
            for i in range(1, 4)],
           [graph.style.line([color.palette.Rainbow])])
    g.writeEPSfile("line")

Since we're plotting a list of data, the style(s) will iterate over
each of its attributes. In the example above, we're using the rainbow
palette as an attribute to generate a color change (note that the
palette is not an attribute itself, but its a valid changeable
attribute). We could also generate our own changeable attribute. For
example we could loop over a list of colors:

    mycolorchanger = attr.changelist([color.rgb.red,
                                      color.rgb.blue,
                                      color.gray(0.5)])

You could use this instead of color.palette.Rainbow in the example
above.

When trying the example you'll note, that the line style is still
changing as well. This is due to the fact, that the attributes are
merged with the default attributes, which consist a line style change
in this case, and this is not affected by the color change at all. So
you may overwrite the line style:

    graph.style.line([style.linestyle.solid, color.palette.Rainbow])

but a better way would be to clear the linestyle by

    graph.style.line([style.linestyle.clear, color.palette.Rainbow])

instead of forcing it.

HTH,

André

PS: I'm aware that there's a lack of proper documentation of all those
    features. We'll try to improve the situation in the future ...

-- 
by  _ _      _    Dr. André Wobst
   / \ \    / )   wobsta@..., http://www.wobsta.de/
  / _ \ \/\/ /    PyX - High quality PostScript figures with Python & TeX
 (_/ \_)_/\_/           visit http://pyx.sourceforge.net/

Hi, thanks a lot for the help. I actually succeeded in changing the color but 
I didn't notice that (due to a silly mistake), my colors only varies between 
gray(1.0) to gray(0.95) which my eyes see as the same color. As result, I 
thought that I misunderstand the docs somehow.

Anyway, I try the color.palette.Rainbow for better colors but It gave a 
ZeroDivisionError. Could you help again this time. Or is it a bug?

Here is the program (the data for one plot are all in one line, x1 y1 x2 
y2    , different lines correspond to different plots, 14 plots in total):

===================================
from pyx import *

g = graph.graphxy(width=8, key=graph.key.key(pos="br"),
        x=graph.axis.log()
)

finfile = open('all.dat')

for i in range(14):
        data= finfile.readline().split()

        d = []
        for idx in range(7,93,4):
                d.append([float(data[idx]),float(data[idx+2])])

        mytitle = "$"+data[1]+"/"+data[2]+"$"

        g.plot(graph.data.list(d, x=1, y=2, title=mytitle),
                        [ graph.style.line( [style.linewidth.THIN,color.palette.Rainbow] ) ]
        )

g.writeEPSfile('EvsG_75.eps')
====================================

And here is the error:

Traceback (most recent call last):

  File "EvsGamma.py", line 32, in ?
    g.writeEPSfile('EvsG_75.eps')
  File "/usr/lib64/python2.3/site-packages/pyx/canvas.py", line 424, in 
writeEPSfile
    abbox = bbox is not None and bbox or self.bbox()
  File "/usr/lib64/python2.3/site-packages/pyx/graph/graph.py", line 496, in 
bbox
    self.finish()
  File "/usr/lib64/python2.3/site-packages/pyx/graph/graph.py", line 436, in 
finish
    self.domethods[0]()
  File "/usr/lib64/python2.3/site-packages/pyx/graph/graph.py", line 323, in 
dolayout
    plotitem.selectstyles(self, styleindex[stylesid(plotitem.styles)], 
styletotal[stylesid(plotitem.styles)])
  File "/usr/lib64/python2.3/site-packages/pyx/graph/graph.py", line 183, in 
selectstyles
    style.selectstyle(privatedata, self.sharedata, graph, selectindex, 
selecttotal)
  File "/usr/lib64/python2.3/site-packages/pyx/graph/style.py", line 471, in 
selectstyle
    privatedata.lineattrs = attr.selectattrs(self.defaultlineattrs + 
self.lineattrs, selectindex, selecttotal)
  File "/usr/lib64/python2.3/site-packages/pyx/attr.py", line 209, in 
selectattrs
    select = a.select(index, total)
  File "/usr/lib64/python2.3/site-packages/pyx/color.py", line 218, in select
    return self.getcolor(index/(total-1.0))
ZeroDivisionError: float division

Hi Toan,

On 13.01.05, Toan T Nguyen wrote:
[ snip ]
> Anyway, I try the color.palette.Rainbow for better colors but It gave a 
> ZeroDivisionError. Could you help again this time. Or is it a bug?
> 
> Here is the program (the data for one plot are all in one line, x1 y1 x2 
> y2    , different lines correspond to different plots, 14 plots in total):
> 
> ===================================
> from pyx import *
> 
> g = graph.graphxy(width=8, key=graph.key.key(pos="br"),
>         x=graph.axis.log()
> )
> 
> finfile = open('all.dat')
> 
> for i in range(14):
>         data= finfile.readline().split()
> 
>         d = []
>         for idx in range(7,93,4):
>                 d.append([float(data[idx]),float(data[idx+2])])
> 
>         mytitle = "$"+data[1]+"/"+data[2]+"$"
> 
>         g.plot(graph.data.list(d, x=1, y=2, title=mytitle),
>                         [ graph.style.line( [style.linewidth.THIN,color.palette.Rainbow] ) ]
>         )
> 
> g.writeEPSfile('EvsG_75.eps')
[ snip traceback ]

The problem is that there is only one data set to be plotted and, thus,
color.palette.Rainbow does not know which color to choose. At the
moment, this leads to a ZeroDivisionError, which is probably not
optimal. Maybe a reasonable choice would be the first color, i.e.,
the one with value=0.

Anyway, to make your example work, just replace color.palette.Rainbow
by an arbitrary color, e.g., color.rgb.red.

        Jörg

Hi,

Could somebody help me exactly how do I change the dash length of linestyle ? 
Thanks a lot.

Toan

Hi,

On 14.01.05, Toan T Nguyen wrote:
> Could somebody help me exactly how do I change the dash length of linestyle ? 
> Thanks a lot.

By using the style.dash attribute:

    c.stroke(path, [style.dash([10])])

HTH,

        Jörg