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MathGroup Archive 2001

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Re: implicit function

  • To: mathgroup at smc.vnet.net
  • Subject: [mg28322] Re: [mg28297] implicit function
  • From: Tomas Garza <tgarza01 at prodigy.net.mx>
  • Date: Wed, 11 Apr 2001 02:01:01 -0400 (EDT)
  • References: <200104070744.DAA02036@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

The answer to FindRoot is in the form of a rule (see Help Browser under this
entry). Look at FullForm:

In[1]:=
FullForm[ff[0.5]]
Out[1]//FullForm=
List[Rule[y, 0.25`]]

You may then use

In[2]:=
ff[.5][[1, 2]]
Out[2]=
0.25

to get your answer the way you want it. Or, you may use ReplaceAll:

In[3]:=
y /. ff[0.5]
Out[3]=
0.25

If you wish to use the same symbol y for the root, you may write

In[4]:=
y = y /. ff[0.5]
Out[4]=
0.25

I know this is a real pain until you get used to it.

Tomas Garza
Mexico City
----- Original Message -----
From: "Phil Bonacich" <bonacich at soc.ucla.edu>
To: mathgroup at smc.vnet.net
Subject: [mg28322] [mg28297] implicit function


> This is a simple problem, but one that has bedeviled me.  I define
> ff[x_] := FindRoot[2y == x, {y, .5}] .  I don't want  "{y -> 0.25}" when I
> enter ff[.5]; I want ".25", so that I can do other things with the
function
> ff.  How do I get it?
>
>



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