Re: Not all points plot on my graph...

*To*: mathgroup at smc.vnet.net*Subject*: [mg105195] Re: Not all points plot on my graph...*From*: "michael.p.croucher at googlemail.com" <michael.p.croucher at googlemail.com>*Date*: Tue, 24 Nov 2009 05:47:29 -0500 (EST)*References*: <hedte4$lsn$1@smc.vnet.net>

On 23 Nov, 11:59, davef <davidfrick2... at yahoo.com> wrote: > Why is it when I write this... > > Clear[f, x] > f[x_] = (x + 2)^(2/3) > Plot[f[x], {x, -3, 0}, PlotRange -> {{-3, 0}, {-4, 4}}] > f[-3] > > .. I get no values show in the graph for x<-2 even though f[-3] > evaluates to (-1)^(2/3). > > (-1)^(2/3) evaluates as f[-3]=1 so why wouldn't the point (-3,1) plot > on my graph? Hi Dave f[-3] isn't 1 - it's -0.5 + 0.866025 I and, since this is a complex number, Mathematica can't plot it on a simply x-y graph Evaluate f[-3] //N to see the complex result for yourself Cheers, Mike www.walkingrandomly.com