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Re: Plot Question

  • To: mathgroup at smc.vnet.net
  • Subject: [mg6839] Re: [mg6797] Plot Question
  • From: Allan Hayes <hay at haystack.demon.co.uk>
  • Date: Tue, 22 Apr 1997 02:33:16 -0400 (EDT)
  • Sender: owner-wri-mathgroup at wolfram.com

"Ivan G. Burch II" <ivanb at hula.net>
[mg6797] Plot Question

>I want to have MMA plot the following:
>
>Plot[{-x^3, -x^(1/3), x}, {x, -10, 10}]
>I get the following errors for this:
>Plot::plnr : -x^(1/3) is not a machine-size number at x = -10
>"       "       "      "  "  "     "   " "    "     " x = -9.18866
>"       "       "      "  "  "     "   " "    "     " x = -8.30382

Ivan:

(-10.0)^(1/3)

	1.07722 + 1.8658 I

This is the default complex value (perfectly correct mathematics).
To get the real values (with Mma 3.0) use

<<Miscellaneous`RealOnly`

Now we get

(-10.0)^(1/3)

	-2.15443
	
and your plot will be as you want

Plot[{-x^3, -x^(1/3), x}, {x, -10, 10}]

Allan Hayes
hay at haystack.demon.co.uk
http://www.haystack.demon.co.uk



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