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MathGroup Archive 2000

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Re: entering an equation

  • To: mathgroup at
  • Subject: [mg21608] Re: [mg21592] entering an equation
  • From: "David Park" <djmp at>
  • Date: Sun, 16 Jan 2000 22:43:53 -0500 (EST)
  • Sender: owner-wri-mathgroup at

>I am trying to plot a series of functions in is giving me
>trouble. I need : ln2 (ln2 x)
>    I enter: Log[2, Log[2,x]]
>and I get:
>is not a machine-size real \
>number at \!\(x\) = \!\(4.1666666666666667`*^-7\)."
>Does anyone have any suggestions?


Plot[Log[2, Log[2, x]], {x, 1.0, 10}]; works but

Plot[Log[2, Log[2, x]], {x, 0.99, 10}]; does not work because you are trying to take
a log of a negative number over the first part of the range.  Mathematica will
produce the plot over the domain where the function is real. So you can either ignore
the error messages, or turn them off, or restrict your plotting domain to a proper
range of numbers which give only real and not complex results.

David Park
djmp at

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