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MathGroup Archive 2000

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RE: newbie PolarPlot question

  • To: mathgroup at smc.vnet.net
  • Subject: [mg25054] RE: [mg25046] newbie PolarPlot question
  • From: "David Park" <djmp at earthlink.net>
  • Date: Thu, 7 Sep 2000 22:27:58 -0400 (EDT)
  • Sender: owner-wri-mathgroup at wolfram.com

Doug,

It would be better to define your function this way...

r[t_] := 16/(5 + 3 Cos[t])

Then

PolarPlot[r[t], {t, 0, 2 Pi}]

works fine. It isn't sufficient to put just r in the PolarPlot. You must
have r[t]. You should probably read over again Section 1.7.1 on Defining
Functions and Section 1.9.1 on Basic Plotting.

As for copying input and output to a posting or email, it is not that
important to have the In[] and Out[] cell labels. In fact, it is probably
better not to have them because then it is easier to copy the statements
back into a Mathematica notebook.

If you convert any input or output cell to InputForm (use Shift-Ctrl-I) it
will then copy into the posting as plain text which can be easily copied
back into a notebook. The 2D formatted input can also be copied back to a
Mathematica notebook and it will display immediately in StandardForm.
However, it is not easy to read in the posting.

David Park
djmp at earthlink.net
http://home.earthlink.net/~djmp/


> -----Original Message-----
> From: Doug Magnoli [mailto:dmagnoli at home.com]
To: mathgroup at smc.vnet.net
> To: mathgroup at smc.vnet.net
> Sent: Sunday, September 03, 2000 10:11 PM> Subject: [mg25054] [mg25046] newbie
PolarPlot question
>
>
> I've defined:
>
> r[t] := 16/(5 + 3 Cos[t])
>
> Then I load Graphics, with:
>
> <<Graphics`
>
> and ask for:
>
> PolarPlot[r, {t, 0, 2 Pi}], which tells me:
>
> ParametricPlot::pptr:
> {r Cos[t], r Sin[t]} does not evaluate to a pair
> of real numbers at t = 2.617993877991494`*^-7
>
>
> Near as I can make out, x and y should both evaluate to real numbers for
> any value of theta between 0 and 2 Pi, so I don't know what I'm doing
> wrong.
>
> ....and, BTW, how do you get all those quotes from mathematica pages into
> this newsgroup without having to edit?  I tried to copy, e.g.,
>
> In[32]:= PolarPlot[4, {t, 0, 2 Pi}]
>
> and I don't get the In[32]:= part.  Also, when copying those error
> messages, I had to edit extensively, or else they look like this when
> copied / pasted:
>
> ParametricPlot::"pptr": "\!\({\(\(r\\ \(\(Cos[t]\)\)\)\), \(\(r\\ \
> \(\(Sin[t]\)\)\)\)}\) does not evaluate to a pair of real numbers at
> \!\(t\) \
> = \!\(2.617993877991494`*^-7\)."
>
> tia,
>
> -Doug Magnoli
>



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