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MathGroup Archive 2005

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Re: a question about plot a list of functions.

  • To: mathgroup at smc.vnet.net
  • Subject: [mg58211] Re: [mg58203] a question about plot a list of functions.
  • From: Bob Hanlon <hanlonr at cox.net>
  • Date: Thu, 23 Jun 2005 05:33:47 -0400 (EDT)
  • Reply-to: hanlonr at cox.net
  • Sender: owner-wri-mathgroup at wolfram.com

Use Evaluate

K=(2 r/(1-r^2))^2;
y=1/(1+K (Sin[x])^2);
y=y/.{r->{0.2,0.9,0.995}};

Plot[Evaluate[y],{x,0,10 Pi}];

or

Needs["Graphics`"];

Clear[y];

y[x_,r_]:=Module[
      {K=(2 r/(1-r^2))^2},
      1/(1+K Sin[x]^2)];

Plot[Evaluate[
      y[x,#]&/@{0.2,0.9,0.995}],
    {x,0,10Pi},
    ImageSize->400,
    PlotStyle->(Hue/@{.6,.4,0}),
    Ticks->{PiScale[0,10Pi,10],Automatic}];


Bob Hanlon

> 
> From: Zhou Jiang <jiangzhou_yz at yahoo.com>
To: mathgroup at smc.vnet.net
> Date: 2005/06/22 Wed AM 01:55:51 EDT
> Subject: [mg58211] [mg58203] a question about plot a list of functions.
> 
> 
> I defined a function as
>  
> K=(2 r/(1-r^2))^2;
> y=1/(1+K (Sin[x])^2);
> y=y/.{r->{0.2,0.9,0.995}}
>  
> Now the result is a list.
> I want to plot y vs. x in one figure and I did the following
>  
> Plot[y, {x, 0, 10 Pi}];
>  
> But Mathematica gave me an error.
> I changed it to
>  
> Plot[{y[[1]], y[[2]], y[[3]]}, {x, 0, 10 Pi}];
>  
> Mathematica gave me a correct plot. Can anyone give me some idea why 
the error message is given by Mathematica since y is a list and nothing is 
diffrent from {y[[1]], y[[2]], y[[3]]}? 
>  
> Thanks.
> 
> 
> 


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