Thanks a lot for all your replies,
I am going to have a look at all this with my teacher and will keep you
posted.
Julien.
2009/11/2 Leo Butler <l.butler at ed.ac.uk>
>
>
> On Mon, 2 Nov 2009, Stavros Macrakis wrote:
>
> < Nice demonstration. But problematic if X (etc.) is an expression, not
> just a variable, so you might want to declare X etc. to be variables.
> <
> < The general case of expressions could also no doubt be fixed using
> patterns, but might be easier to handle using gradef.
> <
> < -s
> <
>
> Thanks, Stavros. I've modified the example as you suggest.
>
> Leo
>
> matchdeclare(X,symbolp,MU,symbolp,SIGMA,symbolp,DUMMY,symbolp);
> tellsimpafter('diff(cdfn(X,MU,SIGMA),X,1),pdfn(X,MU,SIGMA));
>
> tellsimpafter('diff(pdfn(X,MU,SIGMA),DUMMY,1),'diff(pdfn(X,MU,SIGMA),X,1)*diff(X,DUMMY)+'diff(pdfn(X,MU,SIGMA),MU,1)*diff(MU,DUMMY)+'diff(pdfn(X,MU,SIGMA),SIGMA,1)*diff(SIGM\
> A,DUMMY));
> gradef(pdfn(X,MU,SIGMA),
> -(X-MU)/SIGMA^2*pdfn(X,MU,SIGMA),
> -(X-MU)/SIGMA^2*pdfn(X,MU,SIGMA),
> (X-MU)^2/SIGMA^3*pdfn(X,MU,SIGMA));
>
> u : pdfn(x,0,c)/c;
> depends(c,t);
> diff(u,t)-diff(u,x,2);
> subst(c=sqrt(2*t),%);
> ev(%,nouns);
>
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>