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MathGroup Archive 1995

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Re: Plotting

  • To: mathgroup at smc.vnet.net
  • Subject: [mg2163] Re: Plotting
  • From: ianc (Ian Collier)
  • Date: Wed, 11 Oct 1995 01:58:20 -0400
  • Organization: Wolfram Research, Inc.

In article <44qj7k$s22 at ralph.vnet.net>, Julian Charko
<jcharko at microage-ll.awinc.com> wrote:

> In order to plot the function f(x) = a^x, where a<0, over a 
> range of integer values of x, what plotting options would you
> need to use with the Plot command? 
> 
> Specifying a plotting range of real numbers in the usual way,
> as shown below, for example, presents problems because
> Mathematica generates complex numbers for fractional exponents,
> and these obviously cannot be plotted by Plot.
> 
>                  Plot[(-1)^x, {x, -5, 5}]

Well, you could either create a list of the function evaluated 
for integer avlues of x and then use ListPlot to plot it, or
just plot the real part of your function. Both are illustrated
below.

In[6]:=
    pts = Table[{x,(-1)^x}, {x, -5, 5}]
Out[6]=
    {{-5, -1}, {-4, 1}, {-3, -1}, {-2, 1}, {-1, -1}, {0, 1}, 
 
      {1, -1}, {2, 1}, {3, -1}, {4, 1}, {5, -1}}

In[7]:=
    ListPlot[ pts , PlotJoined -> True]

Out[7]=
    -Graphics-

In[8]:=
    Plot[Re[(-1)^x], {x, -5, 5}]

Out[8]=
    -Graphics-

I hope this helps.

--Ian

-----------------------------------------------------------
Ian Collier
Technical Sales Support
Wolfram Research, Inc.
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tel:(217)-398-0700     fax:(217)-398-0747      ianc at wri.com
Wolfram Research Home Page:             http://www.wri.com/
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