On Thu, Aug 21, 2008 at 1:58 PM, Mike Witt <[EMAIL PROTECTED]> wrote: > > This is an attempt to ask my previous question more clearly :-)
I *conjecture* (and definitely could be wrong) that your problem is related to the issue that Sage can plot symbolic functions but constants (rather, numerical constants which have not been coerced to the symbolic expression ring) don't mix well with symbolic expressions. I think this will be fixed soon but don't know what, if any, active trac tickets are related to this. You might try coercing the expressions to the symbolic expression ring (type ?SR for details), assuming the above conjecture is roughly correct. > > I'm looking for a work-around for the situation where I would normally > call parametric_plot (or plot, for that matter) with a function, and in > some particular case that function turns out to evaluate to a constant. > > For example: > > sage: def f(a,b): return e^(a+b*I) > ....: > sage: parametric_plot([real(f(x,1)),imag(f(x,1))], -pi, pi) > > Works as expected > > sage: parametric_plot([real(f(x,-1)),imag(f(x,-1))], -pi, pi) > > Works as expected > > sage: parametric_plot([real(f(x,0)),imag(f(x,0))], -pi, pi) > > Gives a page full of errors, which I interpret to mean that there > was a problem plotting because imag(f(x,0)) evaluates to a constant. > > I believe that this is the same issue described in: > > http://trac.sagemath.org/sage_trac/ticket/2410 > > But I'm not sure. I notice that: > > sage: type(imag(f(x,1))) > <class 'sage.calculus.calculus.SymbolicArithmetic'> > > and: > > sage: type(imag(f(x,0))) > <class 'sage.calculus.calculus.SymbolicConstant'> > > So, perhaps I could use this test (at least in this particular case) to > avoid calling parametric_plot and simply draw a line instead. But > I wonder if there is a more general strategy. For example, a single > test that will tell if a function if going to evaluate to any kind > of "constant" that plot or parametric_plot will have a problem with? > > I'm trying to be as clear as I can about this. I'm very new to Sage, > and I realize that I could be missing something obvious. > > -Mike > > > > > --~--~---------~--~----~------------~-------~--~----~ To post to this group, send email to [email protected] To unsubscribe from this group, send email to [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/sage-support URLs: http://www.sagemath.org -~----------~----~----~----~------~----~------~--~---
