Re: What is this doing...?...

*To*: mathgroup at smc.vnet.net*Subject*: [mg14812] Re: What is this doing...?...*From*: "Allan Hayes" <hay at haystack.demon.co.uk>*Date*: Wed, 18 Nov 1998 01:29:15 -0500*References*: <72je0h$3ep@smc.vnet.net>*Sender*: owner-wri-mathgroup at wolfram.com

Mitch Padua wrote in message <72je0h$3ep at smc.vnet.net>... >I've having some trouble interpreting a graph I receive in mathematica, >maybe someone can help? Here's what I have: > >Normal[Series[Sin[x], {x,0,#}]]& /@ {1,3,5,7} >f[#]& /@ {arg1, arg2, arg3} >Join[{a,b,c}, {d,e}] >plotts[fx_, a0_: 0, {x_,a_,b_}, k_List, opt___] >:=Plot[Evaluate[Join[Normal[Series[fx,{x,a0,#}]]& /@ k, {fx}]], {x,a,b}, >opt] > >now I type the command to graph: > >plotts[Log[x+1], {x, -.99,2}, {1,3,25}, PlotRange->{-5,2}] > >and all is well however when I change the 25 to 30 I get a different >graph, why? What is going on here? I believe this is a Taylor series >or something, but can someone explain to me when I change the >plotts[Log[x+1], {x, -.99,2}, {1,3,25}, PlotRange->{-5,2}] to >plotts[Log[x+1], {x, -.99,2}, {1,3,30}, PlotRange->{-5,2}] I get a >different graph? I must admit I've only used mathematica for about 15 >minutes...so an explanation as to why this graph is changing would >really help. > >Thanks, > >-- >____/| Vincent M. Padua (vpadua at csufresno.edu) \ o.O| > =(_)= "Thou shalt not follow the NULL pointer for > U chaos and madness await thee at its end." > > > Vincent, plotts[Log[x+1], {x, -.99,2}, {1,3,25}, PlotRange->{-5,2}] plots the original function and its power series in x (actually in x-a0, but in the code, a0_: 0 means that if you do not put a0 in, then the default value 0 is used) up to the term in x^1, x^3 and x^25. plotts[Log[x+1], {x, -.99,2}, {1,3,30}, PlotRange->{-5,2}] plots the original function and its power series in x up to the term in x^1, x^3 and x^30 so we get a different plot. To see all the power series that are shown in the previous two plots try plotts[Log[x+1], {x, -.99,2}, {1,3,25, 30}, PlotRange->{-5,2}] Allan --------------------- Allan Hayes Mathematica Training and Consulting www.haystack.demon.co.uk hay at haystack.demon.co.uk Voice: +44 (0)116 271 4198 Fax: +44 (0)870 164 0565