Derivative of an interpol function, what to do with charfun2



El 24/11/13 04:16, ???????? ?????? escribi?:
>
> Thanks, that is indeed what I needed, but now I'm having another 
> problem: i can't make substitution of x for a number in e:
>
> k:ratsubst(x,1,g)$
> e:ratsubst(y,k,e)$
> e(1);
>
> or
>
> y:g;
> e(1);
>
> In e(1) there are still several x'es
>

Make x=1 in g and then force evaluation:

k:''(ratsubst(1,x,g)) $

Calculate e(1) with y=k:

ratsubst(k,y,e(1));


If you want to keep floats,

k:''(subst([x=1], g)) $
subst([y=k], e(1));

--
Mario