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

*To*: mathgroup at smc.vnet.net*Subject*: [mg105209] Re: Not all points plot on my graph...*From*: David Bailey <dave at removedbailey.co.uk>*Date*: Tue, 24 Nov 2009 05:50:13 -0500 (EST)*References*: <hedte4$lsn$1@smc.vnet.net>

davef 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? > > (-1)^(2/3) is a complex number, so you can't plot it on a real plot. Have a look at: (-1)^(2/3)//N and you will see your mistake. David Bailey http://www.dbaileyconsultancy.co.uk