MathGroup Archive 2010

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

Search the Archive

<Null> while building lists

  • To: mathgroup at
  • Subject: [mg112170] <Null> while building lists
  • From: Alessandro <alexxx.magni at>
  • Date: Fri, 3 Sep 2010 06:09:07 -0400 (EDT)

Hi group,
I'm sure I'll bang me on my head as soon as I will Press <Post
but it's since yesterday that I'm struggling with this...

I fast defined this awkward function, to collect the {index,value} of
the maxima of a list of reals (a Fourier transform):

maxima[f_] := Block[{old = f[[1]], m = {}},
  For[i = 2, i < Length[f]/2, i++,
    If[f[[i]] > old && f[[i + 1]] < f[[i]],
     AppendTo[m, {i, f[[i]]}]];
    old = f[[i]]

Problem is, what I get is e.g. this:

> maxima[f]
> {{14 Null, 10.8853 Null}, {21 Null, 3.34261 Null}, {28 Null, 1.47219 Null}}

I'm sure I do not have spaces anywhere (it happened something similar
due to this error, time ago),
so what's wrong?

thanks for any help...


  • Prev by Date: Strange colour highlighting in functions
  • Next by Date: Re: Using ChartStyle
  • Previous by thread: Re: Strange colour highlighting in functions
  • Next by thread: Re: <Null> while building lists