gnuplot-py-users Mailing List for Gnuplot.py

Cecilia Di Chio wrote:
> Hi,
> I've just started to use Gnuplot-py, and I'm having some trouble in
> plotting circles...
> I know that to plot circles in gnuplot one has to use the parametric
> expression x=sin(t) y=cos(t), and then plot [0:2*pi] r*sin(t)+j,
> r*cos(t)+k, where r is the radius and (j,k) the coordinates of the centre...
> My problem is that the radius and the coodinates of the centre are
> "python object" and gnuplot doesn't allow me to use them inside a
> gnuplot call.
> To clarify:
> ...
> for i in range (numOfCircles)
>     r = sizeOfCircle[0,i]
>     j = circlePos[:,i,0]
>     k = circlePos[:,i,1]
> ...
>  
> What I would like to do is
>     g('plot [0:2*pi] r*sin(t)+j, r*cos(t)+k')
> but gnuplot-py doesn't recognise r, j and k ("undefined variable" error).
>  
> Can anyone help me to solve this problem?
> Thanks very much,
> Cecilia

gnuplot is not really a great tool for plotting lots and lots of
circles.  But if you want to do it, you could do something like:


import Gnuplot

circleparams = [
    (0, 0, 1),
    (1, 0, 0.2),
    (0.5, 0, 0.5),
    ]

g = Gnuplot.Gnuplot()

g('set parametric')
g('set trange [0:2*pi]')

plotitems = []
for (x,y,r) in circleparams:
    plotitems.extend([
        Gnuplot.Func('%g + %g*cos(t)' % (x,r,)),
        Gnuplot.Func('%g + %g*sin(t)' % (y,r,)),
        ])

g.plot(*plotitems)
raw_input()


Michael

On Mon, 6 Mar 2006, William Baxter wrote:

>Does gnuplot-py-1.7 only work with Numeric? Are there plans to make it
>compatible with numarray?
>

I use numarray - I just replaced all
import Numeric  => import numarray as Numeric
in the source and it works for me.

I think both Numeric and numarray will be replaced in near future with
numpy, so I would rather have numpy support...

Of course, something like

try:
    import numpy as NumericPackage
except ImportError:
    try:
        import numarray as NumericPackage
    except ImportError:
        try:
            import Numeric as NumericPackage
        except ImportError:
            raise UnholyError, 'numpy, numarray, or Numeric not found.'

would be the best option.

-- 
   Juho Schultz
   e-mail: juh...@as...
   phone:  +358-50-4081854
   web:    www.astro.helsinki.fi/~jschultz
   Observatory
   FIN-00014 University of Helsinki
   FINLAND

Does gnuplot-py-1.7 only work with Numeric? Are there plans to make it
compatible with numarray?

-- 
William T. Baxter, Ph.D.
Wadsworth Center
Empire State Plaza, PO Box 509
Albany, NY 12201-0509

Hi,
I've just started to use Gnuplot-py, and I'm having some trouble in =
plotting circles...
I know that to plot circles in gnuplot one has to use the parametric =
expression x=3Dsin(t) y=3Dcos(t), and then plot [0:2*pi] r*sin(t)+j, =
r*cos(t)+k, where r is the radius and (j,k) the coordinates of the =
centre...
My problem is that the radius and the coodinates of the centre are =
"python object" and gnuplot doesn't allow me to use them inside a =
gnuplot call.
To clarify:
...
for i in range (numOfCircles)
    r =3D sizeOfCircle[0,i]
    j =3D circlePos[:,i,0]
    k =3D circlePos[:,i,1]
...

What I would like to do is
    g('plot [0:2*pi] r*sin(t)+j, r*cos(t)+k')
but gnuplot-py doesn't recognise r, j and k ("undefined variable" =
error).

Can anyone help me to solve this problem?
Thanks very much,
Cecilia


Cecilia Di Chio
Department of Computer Science
University of Essex
Wivenhoe Park
Colchester CO4 3SQ, UK
phone +44 (0)1206 873111
email cd...@es...
http://privatewww.essex.ac.uk/~cdichi/

"If you have a simple idea, state it simply." (W.D. Hamilton)