[Maxima-discuss] Maxima - plot2d: expression evaluates to non-numeric value everywhere in plotting range

[Santiago S. <sse...@gm...>]

I mean to plot a function of one variable, which uses a paramter that is
not included as an argument to the function. Now I want to plot2d the
function, so I mean to assign a temporary value to the parameter for
plotting. I.e.:

   1. Assign parameter value
   2. Plot2d
   3. Forget parameter value

What I did is

> f(u):=a*u;
> a=1;plot2d(f(u),[u,0.2,1]);

but I get the error

> plot2d: expression evaluates to non-numeric value everywhere in plotting range.
> plot2d: nothing to plot.

How would I proceed?

PS: I actually mean to work with functions using many parameters, so if
excluding them as arguments is workable, I'd rather do it for convenience.
Up to now, I have been integrateing, differentiating, factoring, etc., with
no problems.