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a question about plot a list of functions.

• To: mathgroup at smc.vnet.net
• Subject: [mg58203] a question about plot a list of functions.
• From: Zhou Jiang <jiangzhou_yz at yahoo.com>
• Date: Wed, 22 Jun 2005 01:55:51 -0400 (EDT)
• Sender: owner-wri-mathgroup at wolfram.com

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.

• Follow-Ups:
  • Re: a question about plot a list of functions.
    • From: Andrzej Kozlowski <andrzej@akikoz.net>