Extract parameters from FIndFit output

[Frank Letkiewicz]

Is it possible to extract the parameter values generated from FindFIt to
use in other operations?

For example:

xvalues = {3, 5, 12, 47, 81, 112, 129, 186};
yvalues = {0.05, 0.10, 0.25, 0.50, 0.75, 0.90, 0.95, 0.99};
data = Partition[Riffle[xvalues, yvalues], 2];
fitLogNormal = FindFit[data, CDF[LogNormalDistribution[=CE=BC, =CF=83],
x], {=CE=BC, =CF=83}, x]

Out[396]= {=CE=BC -> 3.47733, =CF=83 -> 1.19773}

Can I extract these =CE=BC and =CF=83 values in the output as regular
numbers?

Frank L.

[Sjoerd C. de Vries]

Frank,

There are some strange characters in your post, so I can't read your
variable names, but if the iutput was something like {x->1, y->2} you
can get {1,2} by using ReplaceAll ( /. ):

{x,y} /. {x->1, y->2}

Cheers -- Sjoerd

On Feb 11, 1:14 pm, Frank Letkiewicz <fjl...@mac.com> wrote:
> Is it possible to extract the parameter values generated from FindFIt to
> use in other operations?
>
> For example:
>
> xvalues = {3, 5, 12, 47, 81, 112, 129, 186};
> yvalues = {0.05, 0.10, 0.25, 0.50, 0.75, 0.90, 0.95, 0.99};
> data = Partition[Riffle[xvalues, yvalues], 2];

> fitLogNormal = FindFit[data, CDF[LogNormalDistribution[=CE=BC, =C=

F=83],
> x], {=CE=BC, =CF=83}, x]
>
> Out[396]= {=CE=BC -> 3.47733, =CF=83 -> 1.19773}
>

> Can I extract these =CE=BC and =CF=83 values in the output as reg=
ular
> numbers?
>
> Frank L.

[Bill Rowe]

On 2/11/10 at 5:20 AM, fjl...@mac.com (Frank Letkiewicz) wrote:

>Is it possible to extract the parameter values generated from
>FindFIt to use in other operations?

>For example:

>xvalues = {3, 5, 12, 47, 81, 112, 129, 186}; yvalues = {0.05, 0.10,
>0.25, 0.50, 0.75, 0.90, 0.95, 0.99}; data =
>Partition[Riffle[xvalues, yvalues], 2]; fitLogNormal = FindFit[data,

>CDF[LogNormalDistribution[=CE=BC, =CF=83], x], {=CE=BC, =CF=

=83}, x]

>Out[396]= {=CE=BC -> 3.47733, =CF=83 -> 1.19773}

>Can I extract these =CE=BC and =CF=83 values in the output as

>regular numbers?

Whenever you get a replacement rule, the most direct way to
extract the values is to use it with ReplaceAll (./). For example,

In[9]:= xvalues = {3, 5, 12, 47, 81, 112, 129, 186};

yvalues = {0.05, 0.10, 0.25, 0.50, 0.75, 0.90, 0.95, 0.99};
data = Partition[Riffle[xvalues, yvalues], 2];
fitLogNormal =

FindFit[data, CDF[LogNormalDistribution[m, s], x], {m, s}, x]

Out[12]= {m->3.47733,s->1.19773}

In[13]:= {m, s} /. fitLogNormal

Out[13]= {3.47733,1.19773}

Also, your method of combining xvalues and yvalues works but is
more complex than needed. Much simpler is

data=Transpose@{xvalues, yvalues};

=46or small data sets like you use here, there will be no
significant difference between what you did and using Transpose.
=46or very large data sets, Transpose will be faster.

[Bob Hanlon]

xvalues = {3, 5, 12, 47, 81, 112, 129, 186};

yvalues = {0.05, 0.10, 0.25, 0.50, 0.75, 0.90, 0.95, 0.99};

data = Thread[{xvalues, yvalues}];

You could also use Transpose in place of Thread

data == Transpose[{xvalues, yvalues}]

True

fitLogNormal = FindFit[data,
CDF[LogNormalDistribution[m, s], x],
{m, s}, x]

{m->3.47733,s->1.19773}

fitLogNormal is a list of replacement rules

m /. fitLogNormal

3.47733

fitLogNormal // First // Last

3.47733

Plot[
CDF[LogNormalDistribution[m, s], x] /.
fitLogNormal,
{x, 0, 200},
Epilog -> {Red, AbsolutePointSize[4], Point[data]},
PlotRange -> {0, 1}]

Bob Hanlon

---- Frank Letkiewicz <fjl...@mac.com> wrote:

=============

Is it possible to extract the parameter values generated from FindFIt to
use in other operations?

For example:

xvalues = {3, 5, 12, 47, 81, 112, 129, 186};
yvalues = {0.05, 0.10, 0.25, 0.50, 0.75, 0.90, 0.95, 0.99};
data = Partition[Riffle[xvalues, yvalues], 2];
fitLogNormal = FindFit[data, CDF[LogNormalDistribution[=CE=BC, =CF=83],

x], {=CE=BC, =CF=83}, x]

Out[396]= {=CE=BC -> 3.47733, =CF=83 -> 1.19773}

Can I extract these =CE=BC and =CF=83 values in the output as regular
numbers?

Frank L.

[Arnold Smit]

Frank,

There are some strange characters in your mail, but say your parameters are
called mu and sd, then what you get is a list of rules:
In: fitLogNormal // FullForm
Out: List[Rule[mu, 3.4773291281865117`], Rule[b, 1.1977331975446315`]]

- The first element is a Rule
In: fitLogNormal[[1]] // FullForm
Out: Rule[mu, 3.4773291281865117`]

- You can get to any part of any expression by indexing, f.i.
In: fitLogNormal[[1]][[0]] (* equivalent to fitLogNormal[[1,0]] *)
Out: Rule
In: fitLogNormal[[1]][[1]]
Out: mu
In: fitLogNormal[[1,2]]
Out: 3.47733

- So the simplest way to get to your parameter values is probably:
In: fitLogNormal[[All, 2]]
Out: {3.47733, 1.19773}

Hope this helps, grtz Arnold