Search All of the Math Forum:

Views expressed in these public forums are not endorsed by NCTM or The Math Forum.

Notice: We are no longer accepting new posts, but the forums will continue to be readable.

Topic: Finding Maximum without a plot
Replies: 2   Last Post: Feb 15, 2013 1:56 AM

 Messages: [ Previous | Next ]
 merit_2 Posts: 3 Registered: 4/28/12
Re: Finding Maximum without a plot
Posted: Feb 15, 2013 1:56 AM

New in Mathematica 9 is MaxDetect[].
As an example:

rr = Abs[Zeta[1/2 + I*t]]/t^(1/4)

Abs[Zeta[1/2 + I t]]/t^(1/4)

kk = Table[rr, {t, 1, 1000}] // N;

In[5866]:= MaxDetect[kk, .5]

Out[5866]= {1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 1, 1, 1, 1, \
0, 0, 1, 1, 1, 0, 0, 1, 1, 1, 0, 0, 0, 0, 1, 1, 1, 0, 0, 0, 0, 0, 0, \
0, 0, 1, 1, 0, 0, 0, 0, 1, 1, 0, 1, 1, 0, 0, 0, 0, 0, 0, 0, 1, 1, 0, \
0, 0, 1, 1, 1, 1, 0, 1, 1, 0, 0, 0, 0, 0, 0, 1, 1, 0, 0, 0, 0, 0, 0, \
0, 1, 1, 0, 0, 0, 0, 0, 1, 1, 0, 1}

On Thursday, February 14, 2013 12:09:33 AM UTC-7, Tim Trudgian wrote:
> I should like to find the maximum of
>
>
>
> Abs[Zeta[1/2 + I*t]]/t^(1/4)
>
>
>
> for t large, say, t< 10^10.
>
>
>
> The trouble with NMaximize is that (sometimes) only local maxima are picked up.
>
>
>
> When plotting, say
>
>
>
> Plot[Abs[Zeta[1/2 + I*t]/t^(1/4)], {t, 3, 10^5}, PlotRange -> Full]
>
>
>
> I can see that, around t = 20,000, there is a value above 1.5. This value is not picked up when plotting the same function in the range {t, 3, 10^6}.
>
>
>
> Does anyone have any solutions other than plotting blocks of 10^k, 10^(k+1)?

Date Subject Author
2/15/13 merit_2
2/15/13 Frank K