Re: Series expansion question

*To*: mathgroup at smc.vnet.net*Subject*: [mg122702] Re: Series expansion question*From*: Bob Hanlon <hanlonr357 at gmail.com>*Date*: Mon, 7 Nov 2011 05:50:56 -0500 (EST)*Delivered-to*: l-mathgroup@mail-archive0.wolfram.com*References*: <201111061056.FAA22703@smc.vnet.net>

gts[a, b] /. {a -> x0 + z, b -> y0 + z} Bob Hanlon On Sun, Nov 6, 2011 at 5:56 AM, Recif <recif at yahoo.com> wrote: > I defined a function: > gts[x_, y_] := Normal[Series[g[x, y], {x, x0, 1}, {y, y0, 1}]] > > and when I use it with 'a' and 'b' undefined, I get the value I expect: > gts[a, b] > g[x0,y0] + (a-x0) g^(1,0)[x0,y0] + (b-y0) g^(0,1)[x0,y0] ... > > However when I assign values to a and b: > a = x0 + z > b = y0 + z > > gts[a,b] > gives me an error: > General::ivar: "x0+z is not a valid variable" > > etc. > > I would appreciate any help to fix this. > Thanks. > Recif >

**References**:**Series expansion question***From:*Recif <recif@yahoo.com>