Services & Resources / Wolfram Forums
-----
 /
MathGroup Archive
1998
*January
*February
*March
*April
*May
*June
*July
*August
*September
*October
*November
*December
*Archive Index
*Ask about this page
*Print this page
*Give us feedback
*Sign up for the Wolfram Insider

MathGroup Archive 1998

[Date Index] [Thread Index] [Author Index]

Search the Archive

Re: Result from FindRoot



Torbjrn Randahl wrote:

> How do I use the result from FindRoot in a Plot?
> 
> The resullt from FindRoot is like:
> Out[4]:-> 300 000}
>  how do I assign the result directly to a variable  or  how do I set the
> variable f to the
> resulting (root)?
> 
> i.e I want to change another variable in the expression and then Plot
> the root!

Tobbe:


Plotting:

In[1]:Plot[x/.FindRoot[Tan[x]f, {x,f}], {f,0,Pi/2.1}, PlotRange -> All]


On assinging to variables:

In[2]:FindRoot[Sin[x]0, {x,3}]

Out[2]{x -> 3.14159}

In[3]:newvar /.%

Out[3]3.14159

In[4]:newvar

Out[4]3.14159

More directly

In[5]:newvar2 /.FindRoot[Sin[x]0, {x,3}];

In[6]:newvar2

Out[6]3.14159

We can define a function of parameters

In[7]:root[a_,b_]  :. FindRoot[Sin[x -b]0, {x,a}]

and a version that remembers the answers

In[8]:root2[a_,b_]  :ot2[a,b] . FindRoot[Sin[x -b]0, {x,a}]

In[9]:root2[ 1,4]

Out[9]0.858407

In[10]:?root2

From In[10]:Global`root2
root2[1, 4] .8584073466995231
 
root2[a_, b_] :
  root2[a, b]  /. FindRoot[Sin[x - b] 0, {x, a}] --

Allan Hayes
Mathematica Training and Consulting
Leicester, UK
hay@haystack.demon.co.uk
http://www.haystack.demon.co.uk
voice: +44 (0)116 271 4198
fax: +44 (0)116 271 8642




  • Prev by Date: Re: ContourPlot help
  • Next by Date: fuctional differentiation in Mathematica
  • Prev by thread: Re: Result from FindRoot
  • Next by thread: Calculus Live news release