using plot2d with numerical integration function

Hello,

I probably have a very simple question, but I could not find hints in
the mailing list archive.

I try to plot2d (or wxplot2d) a function containing quad_qad
integration. This numerical function only works, if the variable on the
x achses of my plot is defined. Now plot2d seems to call the function
without defined variable once.

How can I avoid this.

Thanks a lot
Detlef


() ff:(sin(x)^2-1/2)*abs(x-y)*exp(-(x-y)^2/5);
() plot2d(quad_qag(ff,x,-100,100,6),[y,-5,5]);

Maxima encountered a Lisp error:
 Error in FUNCALL [or a callee]: ((MTIMES SIMP) -0.5
                                  ((MEXPT SIMP) 2.7182818284590451
                                   ((MTIMES SIMP) ((RAT SIMP) -1 5)
                                    ((MEXPT SIMP) $Y 2)))
                                  ((MABS SIMP) $Y)) is not of type (OR

RATIONAL

LISP:FLOAT).
Automatically continuing.
To reenable the Lisp debugger set *debugger-hook* to nil.