       Re: Plot[] problem (plnr) - help !!!

• To: mathgroup at smc.vnet.net
• Subject: [mg15992] Re: [mg15935] Plot[] problem (plnr) - help !!!
• From: "Richard Finley" <rfinley at medicine.umsmed.edu>
• Date: Fri, 19 Feb 1999 03:27:08 -0500
• Sender: owner-wri-mathgroup at wolfram.com

```Alexander,

It is not clear to me what you are trying to do??  I presume you mean to
use the assignment operator = instead of the comparator ==??  If
that is true, and I presume you meant to put the Clear[H] before you
define H rather than after??  Even so, you will not be able to plot the
function as is since it has real and imaginary parts.  Instead try this:
a=1
a=.99/50000
H[w_]:= Log[10,Sum[a[k] Exp[I 2 Pi w(-k)], {k,0,1}]]
Plot[Abs[H[w],{w,1,100}]

or you could plot the Real and Imaginary parts separately.  Regards, RF

>>> Alexander Sirotkin <root at borjch.math.tau.ac.il> 02/17/99 10:34PM >>>
Hi.

I'm trying to do most trivial and simple thing - define
some function and then Plot[] it. However, I get some very
weird error - "  ...is not a machine-size real number at ..."

Here is the code :
a==1
a==0.99/50000
H[w] == Log[10,Sum[a[k] Exp[I 2Pi w(-k)], {k,0,1}]]
Clear[H]
Plot[H[w], {w, 1, 100}]

I've seen some articles (even at www.wolfram.com) about that
problem, but NONE of them proposed a working solution !!!

Just putting Evaluate[] inside the Plot[] does nothing...

```

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