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MathGroup Archive 2002

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Re: List argument

  • To: mathgroup at smc.vnet.net
  • Subject: [mg36404] Re: [mg36376] List argument
  • From: BobHanlon at aol.com
  • Date: Wed, 4 Sep 2002 21:22:19 -0400 (EDT)
  • Sender: owner-wri-mathgroup at wolfram.com

In a message dated 9/4/02 3:31:53 AM, pascal at go.ro writes:

>I want to do these operations:
>
>eq = m x^2 + 2(m + 1)x + m + 2
>l = {}
>For[i = -30, i < 30, i++, AppendTo[l, eq /. m -> i]]
>Plot[l, {x, -50, 50}]
>
>but i get this error:
>l is not a machine-size real number at x = -49.99999583333334
>
>Can someone exaplain to me what i am doing wrong here??
>

eq = m x^2 + 2(m + 1)x + m + 2;
l = {};
For[i = -30, i < 30, i++, AppendTo[l, eq /. m -> i]];

It would be more straightforward and efficient to define the list using Table

l == Table[eq, {m, -30, 29}]

True

To Plot, use Evaluate

Plot[Evaluate[l], {x, -50, 50}];


Bob Hanlon


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