[PyX-user] No horizontal line.

[Andrea R. <ari...@pi...>]

Hi,
I was trying a simple plot, when I realized that PyX doesn't allow to  
plot horizontal line expressed as analitic function. Here it is a  
simple example:

> In [197]: h = pyx.graph.graphxy(width = 10, height = 10, x =  
> pyx.graph.axis.lin(min = 0, max = 10), y = pyx.graph.axis.lin(min = 0,  
> max = 10))
>
> In [198]: h.plot(pyx.graph.data.function("y = x"))
> Out[198]: <pyx.graph.graph.plotitem instance at 0x6e80558>
>
> In [199]: h.plot(pyx.graph.data.function("y = 2"))
> ----------------------------------------------------------------------- 
> ----
> ValueError                                Traceback (most recent call  
> last)
>
> /Users/andrea/Documents/Dottorato/Working/<console>
>
> /sw/lib/python2.3/site-packages/pyx/graph/graph.py in plot(self, data,  
> styles)
>     231         plotitems = []
>     232         for d in usedata:
> --> 233             plotitems.append(plotitem(self, d, styles))
>     234         self.plotitems.extend(plotitems)
>     235         if singledata:
>
> /sw/lib/python2.3/site-packages/pyx/graph/graph.py in __init__(self,  
> graph, data, styles)
>     170
>     171         # perform setcolumns to all styles
> --> 172         self.data.initplotitem(self, graph)
>     173         columns = self.data.getcolumnnames(self)
>     174         usedcolumns = []
>
> /sw/lib/python2.3/site-packages/pyx/graph/data.py in  
> initplotitem(self, plotitem, graph)
>     617                     raise ValueError("multiple variables  
> found")
>     618         if self.xname is None:
> --> 619             raise ValueError("no variable found")
>     620         plotitem.columns = {self.xname: 0, self.yname: 1}
>     621
>
> ValueError: no variable found

There is a trick that I can use to get the desired result? Could this  
feature be embeded in a future version of PyX?

Thanks,
  Andrea.