How does ilt get the terms to take back to time space. It would seem
that it must use what you supplied, or does it use the residue function?
Thanks for your reply
Doug Stewart
Richard Fateman wrote:
>
> Partfrac solves a given problem over the rational numbers,
> not the (approximate) real numbers.
>
> If you really want the (numeric, approximate) partial
> fraction expansion, that can be computed, but partfrac doesn't do that.
>
>
> See note below yours, for a program, fpfe, that does this.
>
> (C8) fpfe(d1,s);
> 1.677050983124843 1.677050983124843
> (D8) --------------------- - ---------------------
> s + 2.105572809000084 s + 3.894427190999916
> (C9)
> .... keepfloat:true$
> ratsimp(d8); gives
> almost the same as what you started with.
> But not exactly.
> RJF
>
> PS, as far as I know, this is not in the "share" directory. But
> it could be put there. LLGPL.
>
>
>
>
> Doug Stewart wrote:
>
>>>>
>> partfrac ( +3 /(s^2 +6*s +8.2),s) ;
>>
>> Since this has 2 real roots I would expect two terms in the answer
>> but I get only 1.
>> how do you make it give the two terms?
>> Doug Stewart
>>
>> _______________________________________________
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>> Maxima@math.utexas.edu
>> http://www.math.utexas.edu/mailman/listinfo/maxima
>
>
>
> fpfe(p,x):=
> block ([num, den,div, res,keepfloat:true,lroots,distinctroots,qq, L,
> c],
> local(r,q),
> p:rat(p), num:ratnumer(p), den:ratdenom(p), div: divide(num,den),
> res: ratdisrep(div[1]),
> num: ratdisrep(div[2]/ratcoef(den,x^hipow(den,x))),
> lroots:map(rhs,allroots(den)),
> r[i]:=0, for c in lroots do r[c]:r[c]+1,
> distinctroots: map(first,rest(arrayinfo(r),2)),
> qq:1,
> for c in distinctroots do qq:qq*(x-c)^r[c],
> for c in distinctroots do q[c]:qq/(x-c)^r[c],
> for c in distinctroots do for i: 1 thru r[c] do
> res: res+1/(r[c]-i)!
> *ratsimp(subst(c,x,diff(num/q[c],x,r[c]-i)))
> /(x-c)^i,
> return(res));
>
>
>
> /*
> Published in Proc. ISSAC'82, "Computer Algebra and Numerical
> Integration," by R. Fateman p 228 - 232 */
>
> _______________________________________________
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> Maxima@math.utexas.edu
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>