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[Maxima-bugs] [ maxima-Bugs-1692729 ] coeff, ratcoef on Taylor series around inf
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From: SourceForge.net <no...@so...> - 2007-04-05 05:45:54
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Bugs item #1692729, was opened at 2007-04-02 04:46 Message generated for change (Comment added) made by macrakis You can respond by visiting: https://sourceforge.net/tracker/?func=detail&atid=104933&aid=1692729&group_id=4933 Please note that this message will contain a full copy of the comment thread, including the initial issue submission, for this request, not just the latest update. Category: None Group: None Status: Open Resolution: None Priority: 5 Private: No Submitted By: Nobody/Anonymous (nobody) Assigned to: Nobody/Anonymous (nobody) Summary: coeff, ratcoef on Taylor series around inf Initial Comment: It seems that coeff() and ratcoef() have trouble extracting coefficients from Taylor expansions around infinity: (%i119) taylor(1/x, x, inf, 1); 1 (%o119)/T/ - + . . . x (%i120) ratcoef(taylor(1/x, x, inf, 1), x, -1); (%o120)/R/ 0 (%i121) coeff(taylor(1/x, x, inf, 1), x, -1); (%o121)/R/ 0 A work-around is to get rid of the Taylor property, e.g., by wrapping the expression in subst(0, 0, ...). ---------------------------------------------------------------------- >Comment By: Stavros Macrakis (macrakis) Date: 2007-04-05 01:45 Message: Logged In: YES user_id=588346 Originator: NO Yes, ratcoeff is a bit confused by taylor expansions at infinity: qq: taylor(sum((i-3+100)*x^(i-3),i,0,5),x,inf,10) => 102*x^2+101*x+100+99/x+98/x^2+97/x^3 + ... makelist(ratcoeff(qq,x,i),i,-3,4) => => [0, 102, 101, 100, 99, 98, 97, 0] In other words, it treats the 1/x^2 as the ratcoeff(...,x,2) term. So the workaround is to negate the power... but of course that will become exactly wrong when the bug is fixed.... ---------------------------------------------------------------------- You can respond by visiting: https://sourceforge.net/tracker/?func=detail&atid=104933&aid=1692729&group_id=4933 |
