Re: FindRoot for the determinant of a matrix with a varying size
- To: mathgroup at smc.vnet.net
- Subject: [mg59734] Re: [mg59720] FindRoot for the determinant of a matrix with a varying size
- From: Bob Hanlon <hanlonr at cox.net>
- Date: Fri, 19 Aug 2005 04:31:59 -0400 (EDT)
- Reply-to: hanlonr at cox.net
- Sender: owner-wri-mathgroup at wolfram.com
f[x_?NumericQ]:=Det[Table[Exp[(i-j)/x]/x,{i,2,5,x},{j,2,5,x}]];
FindRoot[f[x]==0.1,{x,5}]
{x -> 10.}
Bob Hanlon
>
> From: "Wonseok Shin" <wssaca at gmail.com>
To: mathgroup at smc.vnet.net
> Date: 2005/08/18 Thu AM 12:17:48 EDT
> Subject: [mg59734] [mg59720] FindRoot for the determinant of a matrix with a varying
size
>
> Hello everyone,
>
> I am a user of Mathematica 5.1 for Mac .
> I defined the function using the determinant of a matrix of a varying
> size. Even though this function is well-behaving, it seems that
> FindRoot cannot deal this function. Please look at the following code:
>
> -------------------------------------------------
> In[1]:=
> f[x_] := Det[Table[Exp[(i - j)/x]/x , {i, 2, 5, x}, {j, 2, 5, x}]]
>
> In[2]:=
> Plot[f[x], {x, 3, 30}]
> -------------------------------------------------
>
> By running the above Plot command, you can see clearly that the
> function f is very smooth in the interval 3< x < 30, and f[x] == 0.1
> has a solution in 5 < x < 15.
>
> But I've failed to find a solution of f[x] == 0.1 using FindRoot:
>
> -------------------------------------------------
> In[3]:=
> FindRoot[f[x] == 0.1, {x, 5}]
>
> Table::iterb : Iterator {i, 2, 5, x} does not have appropriate bounds.
> -------------------------------------------------
>
> Is there any workaround for this problem?
>
> Thanks,
>
> Wonseok Shin
>
>