Re: Plot and evaluate help

*To*: mathgroup at smc.vnet.net*Subject*: [mg7874] Re: [mg7839] Plot and evaluate help*From*: "Eric P. Nichols" <raoul at montana.campus.mci.net>*Date*: Thu, 17 Jul 1997 15:35:38 -0400*Sender*: owner-wri-mathgroup at wolfram.com

> I am a novice mathematica user having difficulty plotting a > simple > function. I am trying to plot the functions f[x_] = c1 / (c1 + c2) > and f'[x_] > over an arbitrary range for c1 and c2. The Plot syntax specifies > Plot[f, {x, > min, max}]. I hate to ask such a basic question, but how does one > plot a > function of more than one variable? Alan, The function you need is Plot3D, the syntax is: Plot3D[f, {x, xmin, xmax}, {y, ymin, ymax}] In your case, then, you could write: f = c1 / (c1 + c2) Plot3D[f, {c1, -5, 5}, {c2, -5, 5}] There are two different partial derivatives, given by f1 = D[f, c2] f2 = D[f, c2] then you can Plot3D f1 and f2 as well. If you want to use f, f1, and f2 in different ways, you may want to define a function, f[c1_, c2_] := c1 /(c1 + c2) Then you can type f[1,1] and get the response 0.5, for example, or do the plots like: Plot3D[f[c1, c2], {c1, -5, 5}, {c2, -5, 5}] notice now you need to say f[c1, c2], not just f. Hope this helps, Eric --------------8CC25950981C632CB88A1086 Content-Description: Card for Eric Nichols Content-Disposition: attachment; filename="vcard.vcf" begin: vcard fn: Eric Nichols n: Nichols;Eric email;internet: raoul at montana.campus.mci.net x-mozilla-cpt: ;0 x-mozilla-html: TRUE end: vcard --------------8CC25950981C632CB88A1086--