Re: [Please Help] How to get coefficient list from a

*To*: mathgroup at smc.vnet.net*Subject*: [mg114428] Re: [Please Help] How to get coefficient list from a*From*: =?tis-620?b?zdTKw+zD0aqq7CCiqMPD2OinyA==?= at smc.vnet.net*Date*: Sat, 4 Dec 2010 06:13:05 -0500 (EST)

Thank you for your answer. But I would like only the coefficient of series equation in the form {a1, a2 , a3 ,a4,a5,a6} not to be in the form of {{a1, a3, a6}, {a2, a5, 0}, {a4, 0, 0}}. How to get there? Best regard 2010/12/3 Bob Hanlon <hanlonr at cox.net> > > expr1 = a1 + a2*x + a3*y + a4*x^2 + a5*x*y + a6*y^2; > > coef = CoefficientList[expr, {x, y}] > > {{a1, a3, a6}, {a2, a5, 0}, {a4, 0, 0}} > > From example in documentation on CoefficientList > > expr2 = Fold[FromDigits[Reverse[#1], #2] &, coef, {x, y}] > > a1 + a2 x + a4 x^2 + (a3 + a5 x) y + a6 y^2 > > expr1 == expr2 // Simplify > > True > > > Bob Hanlon > > ---- Autt <kajornrungsilp.i at gmail.com> wrote: > > ============= > Greeting, > I've a list issued from multivariate series like : K={a1+a2*x +a3*y > +a4*x^2*+a5*x*y +a6*y^2 } > I need to have {a1, a2 , a3 ,a4,a5,a6} > > How to do that please? > e.g. > n = 3 > u = Normal[Series[x^4 + y^4 + x^2, {x, 5, n}, {y, 5, n}]] > c[0] = {}; > d = {}; > q[0] = {}; > For[k = 1 , k <= n - 1, k++, > For[i = 0 , i <= k , i++, > p[i, k - i] = > SeriesCoefficient[u, {x, 5, i}, {y, 5, k - i}]; > q[k] = Union[{q[k - 1], {p[i, k - i]}}]; > d = Union[d, q[k]]; > > Print[d]; > > Best regard, > > > > > -- > > Bob Hanlon > >