       Re: Plot, Cursor and Spelling Errors questions

• To: mathgroup at smc.vnet.net
• Subject: [mg14434] Re: [mg14393] Plot, Cursor and Spelling Errors questions
• From: "Jens-Peer Kuska" <kuska at linmpi.mpg.de>
• Date: Wed, 21 Oct 1998 03:32:30 -0400
• Sender: owner-wri-mathgroup at wolfram.com

```Hi Ranko,

1) Mathematica can't draw the difference because You typed P[x]
(CapitalP) but
you have only defined p[x_] (small p)

Plot[Evaluate[f[x]-p[x]], {x,-1, 1}, PlotPoints -> 50];

and all works fine.
2) Put  the commands

Off[General::spell]
Off[General::spell1]

at the top of Your notebook and You will never see the messages again.

Hope that helps
Jens

-----Original Message-----
From: Ranko Bojanic <bojanic at math.ohio-state.edu> To:
mathgroup at smc.vnet.net
Subject: [mg14434] [mg14393] Plot, Cursor and Spelling Errors questions

>Dear Mathematica friends:
>
>I am having problems when trying to plot the graph of an error curve
>when the magnitude of the error curve is close to the \$MachineEpsilon
>number. The following example is typical:
>
>n = 15;
>f[x_] := Exp[x];
>xLst = Table[Cos[((2*k - 1)*Pi)/(2*n)], {k, 1, n}]//Reverse; yLst =
>N[Map[f,xLst], 30];
>fLst = Transpose[{xLst, yLst}];
>p[x_] := InterpolatingPolynomial[fLst, x]; Plot[Evaluate[f[x]-P[x]], {x,
>-1, 1}, PlotPoints -> 50];
>
>Why the Plot function cannot draw the graph of the difference? I can
>still get a graph by computing 1000 points on the error curve and using
>ListPlot with PlotJoined->True, but the graph is not very smooth.
>
>The problem here is not in the accuracy of computations, as the ListPlot
>function shows, but in the way Plot processes data. Is there a way to
>force Plot to draw the error curve correctly?
>
>An unrelated programming question:While  Mathematica is doing a lengthy
>computation, I would like to change the cursor into a watch cursor. I
>could not find any information on how to do it. Is there a simple
>command to change the current cursor into a watch cursor - something
>like SetCursor and InitCursor in Pascal.
>
>Last question: If you run the program listed here, you will probably get
>the messages :
>General::spell:Possible spelling error: new symbol "yLst" is similar
>                       to existing symbol {xLst} General::spell:Possible
>spelling error: new symbol "fLst" is similar
>                       to existing symbol {xLst,yLst}
> Is there a way to turn off these spelling errors messages?
>
>Thanks,
>Ranko Bojanic
>bojanic at math.ohio-state.edu
>
>
>

```

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