Thanks, Waldek - that works fine! I am reconsidering FriCAS for some work. One problem I've had is with multivariate polynomials, say in the variables a,b,c,x,y,z. What I've needed to do is to rewrite the polynomial in the variables x,y,z so the coefficients are themselves polynomials in the other variables (a,b,c). Neither Maxima nor Sage can manage this particularly well. But with FriCAS it's very simple:
coefficients(p::DMP([x,y,z], POLY INT) and I have exactly what I want. -Alasdair On Sunday, January 19, 2014 10:51:03 PM UTC+11, Alasdair wrote: > > Hello, > > I last used Axiom about 8 years ago, and I haven't kept up either with it > or its forks much since then. (I'm listed as a contributor at > http://www.axiom-developer.org/axiom-website/community.html). Anyway, > I've since forgotten pretty all I knew (which was never much); in > particular how best to manipulate types. > > Just today I downloaded the source of FriCAS and compiled it. > > Here's my first question. I am experimenting with formal derivatives. So: > > f := operator 'f >> y := operator 'y >> f1 := D(f(x,y(x)),x) >> f1 := subst(f1,D(y(x),x)=f(x,y(x))) >> > > This looks fine so far. However, eventually I want to do some algebraic > manipualtion on these (and higher) derivatives, for which it will be > convenient to replace derivatives in these expressions with a simple > symbol. For example: > > f2:=D(f1,x) >> f2:=subst(f2,D(y(x),x)=f(x,y(x))) >> message(unparse(f2::InputForm))$OutputForm >> >> >> D(D(f(x,y(x)),x::Symbol),x::Symbol)+(f(x,y(x))^2*D(D(f(x,y(x)),y(x)::Symbol), >> >> y(x)::Symbol)+(f(x,y(x))*D(D(f(x,y(x)),y(x)::Symbol),x::Symbol)+(f(x,y(x))*D( >> >> D(f(x,y(x)),x::Symbol),y(x)::Symbol)+(D(f(x,y(x)),y(x)::Symbol)*D(f(x,y(x)),x >> ::Symbol)+f(x,y(x))*D(f(x,y(x)),y(x)::Symbol)^2)))) >> > > (I filched the "message" command from the Axiom newsgroup archive.) What > I want to do is something like > > subst(f2,D(D(f(x,y(x)),x),x)=Fxx) >> > > so that in my final expression the symbol "Fxx" will take the place of > D(D(f(x,y(x)),x::Symbol),x::Symbol) in the above output expression. This > is going to require some coercion... but I'm not sure how. Any ideas? > > Second question: the Axiom pages say that Hyperdoc is being replaced with > a help browser under Firefox. I like the idea of this very much: Hyperdoc > always seemed a bit clumsy to me. Is this available in FriCAS, and if so, > how? > > Thanks, folks! > > -Alasdair > -- You received this message because you are subscribed to the Google Groups "FriCAS - computer algebra system" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To post to this group, send email to [email protected]. Visit this group at http://groups.google.com/group/fricas-devel. For more options, visit https://groups.google.com/groups/opt_out.
