Re: Log(ln) Function + 2 Parameters + Greater

*To*: mathgroup at smc.vnet.net*Subject*: [mg89301] Re: Log(ln) Function + 2 Parameters + Greater*From*: Bill Rowe <readnews at sbcglobal.net>*Date*: Wed, 4 Jun 2008 05:38:11 -0400 (EDT)

On 6/3/08 at 3:59 AM, vexie.infamous at googlemail.com (Felipe Mannshardt) wrote: >i am having problem telling Mathematica to: >First Try, >Clear[x, f] f[x_] := x (a + Log[x])^2 >a > 0 Plot[f[x], {x, -5, 5}] >Second Try, >f[x_] := x (a + Log[x])^2 >Plot[f[x], {x, -5, 5}] /.a-> a>0 Neither of the above will work since in neither case does your function return a numeric value. Plot can only plot functions that return numeric values. >What i want is to tell Mathematica to draw a Graph of f[x] when a>0 There are several possible ways to go depending on what it is you have in mind. You could plot a family of curves for different a values, i.e., Plot[Table[x (a + Log[x])^2, {a,0,1,.2}],{x,.1,3.5}] you could plot a surface, i.e., Plot3D[x (a + Log[x])^2, {x,.1,3.5},{a,0,1}] or either create a DensityPlot or ContourPlot by using these in place of Plot3D or you could show a region doing Plot[{5, x*Log[x]^2}, {x, 0.1, 3.5}, Frame -> True, PlotRange -> {-0.5, 5}, Axes -> None, Filling -> {1 -> {2}}]