Here's a sort of hybrid solution, using odeint but then converting out
of the numpy types.
T_steam = 250.0
UA = 10.0
M = 1000.0
W = 100.0
Cp = 2.0
To = 20.0
import numpy
from scipy.integrate import odeint
def dTdt(T,t):
dT1dt = (W*Cp*(To-T[0])+UA*(T_steam-T[0]))/(M*Cp)
dT2dt = (W*Cp*(T[0]-T[1])+UA*(T_steam-T[1]))/(M*Cp)
dT3dt = (W*Cp*(T[1]-T[2])+UA*(T_steam-T[2]))/(M*Cp)
return numpy.array([dT1dt, dT2dt, dT3dt], dtype=float)
t = numpy.arange(0r,200r,1r,dtype=float)
T_int = numpy.array([20.0r,20.0r,20.0r],dtype=float)
T = odeint(dTdt,T_int,t)
sdata = [[float(y) for y in x] for x in T.transpose()]
plots = [list_plot(x, plotjoined = True, rgbcolor = hue(sdata.index(x)/
3,1,1)) for x in sdata]
show(sum(plots), axes_labels=['t','Temperature'], ymax = 60)
There is some work being done on improving support for plot legends
and better axes in Sage (by A. Bergeron and M. Hansen I believe);
right now sometimes its necessary to add text more directly with the
"text" command (produces a graphics object you can add to other
graphics).
Hope that helps,
M. Hampton
On Feb 17, 12:25 am, Steve Yarbro <[email protected]> wrote:
> Hi Mike:
>
> Wow, thanks for the very timely response, that was warp speed. I've tried
> your suggestion and I've stopped having the error message, but for some
> reason, I don't get a plot. I'm a newbie with Python coming from the MATLAB
> world. I'll keep working with it, but here is what I have:
>
> t = arange(0r,200r,1r)
> T_int = array([20.0r,20.0r,20.0r])
>
> T = odeint(dTdt,T_int,t)
>
> plot(t,T)
> xlabel('t')
> ylabel('Temperature')
>
> When I evaluate, I get the following:
>
> Text(0.5,0.5,'Temperature')
>
> Would a better approach be to use the ode_solver from Sage?
>
> On Mon, Feb 16, 2009 at 2:17 PM, Mike Hansen <[email protected]> wrote:
>
> > Hello,
>
> > This is due to the interaction between numpy/scipy and Sage's
> > datatypes. See my response at
>
> >http://groups.google.com/group/sage-devel/browse_thread/thread/7038a4...
>
> > --Mike
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