#2679 fails to changevar

None
closed
nobody
None
5
2014-02-18
2014-01-19
dan hayes
No

changevar command
wxMaxima version: 13.4.0
Maxima version: 5.31.1
Maxima build date: 2013-09-24 09:49:12
Host type: i686-pc-mingw32
Lisp implementation type: GNU Common Lisp (GCL)
Lisp implementation version: GCL 2.6.8

(n:2,assume(m>0),assume(u>0),assume(w>0),assume(a>0),assume(r>0),for i thru n do(assume(a[i]>0),assume(r[i]>0) ,assume(u[i]>0),assume(w[i]>0)
,for j thru n do(assume(a[i,j]>0),assume(r[i,j]>0) ,assume(u[i,j]>0),assume(w[i,j]>0))),lisv:makelist([x[1,j],x[2,j]],j,1,3),tt:product( exp(-%i*(w[1,j]*x[1,j]
+w[2,j]*x[2,j])-a[1]*(x[1,j]^2+x[2,j]^2) -u^2*(x[1,j]-x[2,j])^2),j,1,3),t:tt,for i thru 2 do for j thru 3 do t:integrate(t,lisv[j][i],-inf,inf),t:integrate(t,u,0,inf)
,ldisp([t]),chanagevar(t,u^4/(8*a[1]*u^4+12*a[1]^2*u^2+4*a[1]^3)-y,y,u));

As one will see the changed to variable has a straightforward solution in terms of the new variable y and getting u back as a function of y. But maxima will not do it
but only outputs the trivial command back again without any evaluation or putting
the integral in terms of the new variable y as it is supposed to do.

Discussion

    • status: open --> pending
     
  • This is probably because of a typo (chanagevar). I've just reformatted your example and run it here and it's not managed to return yet. This is arguably not helpful behaviour, but maybe you're just asking Maxima to do an unreasonably hard calculation: I don't know.

    Anyway, I'm pretty certain that this bug report is because of an error so I'm marking it pending. Please close if I'm correct.

     
    • status: pending --> closed
     
  • Since there hasn't been any response on this pending ticket, and I don't believe there's a bug here, I'm going to close it.

    Please reopen if this is wrong.