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

  • To: mathgroup at smc.vnet.net
  • Subject: [mg89318] Re: Log(ln) Function + 2 Parameters + Greater
  • From: Bill Rowe <readnews at sbcglobal.net>
  • Date: Thu, 5 Jun 2008 00:44:41 -0400 (EDT)

On 6/4/08 at 5:37 AM, vexie.infamous at googlemail.com (Felipe
Mannshardt) wrote:

>Thanks for all replies, worked for my last function, but the
>suggestions you guys made so far did work with my last function, but
>now i have a new one, and i am here just playing around and i am
>unable to get it drawn :(

>First to the first Function, i believe the best suggestion was the
>use of "if",

>But, i can not get it to work :/

>Clear[x, f, a]
>f[a_][x_] := x (a + Log[x])^2
>If[a > 0, Plot[f[x], {x, 0, 2}]]

Since a is not defined, Mathematica cannot determine whether a
is greater than zero or not. Consequently, the If statement is
returned unevaluated.

>And all suggestions also did not work at all for my new Function,

>f[a_][x_] := (x/E^(ax));
>Plot[Table[f[a, x], {a, 0, 2}], {x, 0, 3}]

>What am i doing wrong ?

Simply put you are not being consistent. If you define f using
the form f[a_][x_] then you need to use this form when plotting.
That is,

f[a_][x_] := (x/E^(ax));
Plot[Table[f[a][x], {a, 0, 2}], {x, 0, 3}]

should give you the plot you are expecting. Or you could get the
same result with


f[a_, x_] := (x/E^(ax));
Plot[Table[f[a, x], {a, 0, 2}], {x, 0, 3}]

Notice, I use the same form for Plot as I used to define the function.


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