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MathGroup Archive 1998

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Re: Why doesn't this work ?



Andreas,

it is the Plot[ ] that needs a in-place Evaluate command: (see help file
:
"Plot evaluates its arguments in a nonstandard way (see
SectionA.4.). You
should use Evaluate to evaluate the function to be plotted if this can
safely
be done before specific numerical values are supplied. ")

In[7]:Clear[S2];
  S2¼in[x],Cos[x]};
  Plot[Evaluate@S2, {x, 0, Pi}]
In[12]:Clear[S,dx,S3,x];Remove[S3]
  S[x_]:¼in[x/dx], Cos[x/dx], Sin[2*x/dx]};
  S3[x] /. dx -> 2;
  Plot[Evaluate@S3, {x, 0, Pi}]

wouter.


At 04:10 12-01-98 -0500, Andreas Keese wrote:
>Look at this:
>
>This works:
>  Clear[S1];
>  S1Ān[x];
>  Plot[S1, {x, 0, 3}]
>
>But why doesn't it work with more than one functions ?
>
>  Clear[S2];
>  S2¼in[x],Cos[x]};
>  Plot[S2, {x, 0, Pi}]
>
>gives an error - Mathematica complains that S2 is not a machine-size
>number.
>
>BTW: I don't want S2 to be pattern cause I want to use this as follows:
>
>  Clear[S,dx,S3,x];
>  S[x_]:¼in[x/dx], Cos[x/dx], Sin[2*x/dx]};
>  S3ļaluate[S[x] /. dx -> 2];
>  Plot[S3, {x, 0, Pi}];
>
>
>Bye,
>Andreas
>
>
Dr. Wouter L. J. MEEUSSEN
w.meeussen.vdmcc@vandemoortele.be
eu000949@pophost.eunet.be




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