Re: minmum of a function
- To: mathgroup at smc.vnet.net
- Subject: [mg75126] Re: minmum of a function
- From: Jean-Marc Gulliet <jeanmarc.gulliet at gmail.com>
- Date: Wed, 18 Apr 2007 04:57:15 -0400 (EDT)
- Organization: The Open University, Milton Keynes, UK
- References: <f014ar$8qr$1@smc.vnet.net>
skruege at gwdg.de wrote:
> Thank you for your help concerning the minimum of a function.
>
> I have another little problem, I cannot solve:
>
> At one point in my simulation I put
>
> t1 := Table[amp[a], {a, 0.1, 0.3, 0.1}]
> Evaluate[t1]
>
> and I get out
>
> {{0.270697, {0.909768 (p -> -0.15708)}}[0.1], {0.270697, {0.837837 (p ->
> -0.314159)}}[0.2], {0.653976, {0.782008 (p -> -0.471239)}}[0.3]}
>
> Now, for t1[[1,1]]
>
> I get out
>
> [0,1]
>
> and not 0.270697 as I hoped.
>
> Apparently {0.270697, {0.909768 (p -> -0.15708)}} is not an element of the
> list.
>
> Ist it possible to read out the first numbers of the different {}-brackets
> (0.270697, 0.270697 and 0.653976) anyway?
>
> Sven Krueger
Hi Sven,
(Head /@ t1)[[All,1]]
will do it.
Now the question is: Are you sure that the format of the list t1 is
really the one you want? As defined (or returned by amp[a]), t1 is a
list of expressions with _head_ of the form {aNumber, {anotherNumber *
aRule}}. Therefore, the elements that Part sees by default are 0.1, 0.2,
etc.
In[1]:=
t1 = {{0.270697, {0.909768*(p -> -0.15708)}}[0.1],
{0.270697, {0.837837*(p -> -0.314159)}}[0.2],
{0.653976, {0.782008*(p -> -0.471239)}}[0.3]};
In[2]:=
t1[[1]]
Out[2]=
{0.270697, {0.909768*(p -> -0.15708)}}[0.1]
In[3]:=
Head[t1[[1]]]
Out[3]=
{0.270697, {0.909768*(p -> -0.15708)}}
In[4]:=
Head[t1[[1]]][[1]]
Out[4]=
0.270697
In[5]:=
(Head /@ t1)[[All,1]]
Out[5]=
{0.270697, 0.270697, 0.653976}
You may prefer to check your function amp[] and fix it so it will return
its results as a list of values.
Regards,
Jean-Marc