       Re: [Q] Plotting non-continuous function

• To: mathgroup at smc.vnet.net
• Subject: [mg4478] Re: [Q] Plotting non-continuous function
• From: rubin at msu.edu (Paul A. Rubin)
• Date: Mon, 29 Jul 1996 02:37:29 -0400
• Organization: Michigan State University
• Sender: owner-wri-mathgroup at wolfram.com

```In article <4s4itn\$9ud at dragonfly.wolfram.com>,
pherron at GSB-Pound.Stanford.EDU (Michael C. Herron) wrote:
->
->Suppose I have defined:
->
->f[x_] := Which [x<=5,2,True,10]
->
->If I then do Plot [f[t],{t,0,20}], the resulting graphic has a
->vertical line at x=5.  Is there anyway to avoid this?  Ideally, I
->would like the plot to have an open ball on the line y=2 and a closed
->ball at y=10 to indicate that the function at x=5 has a limit from the
->right but not from the left.  Is it possible to do this?  If the
->answer is in a mathematica book, I would like a reference.
->
->Thanks.
->
->Michael

You can always split the function into two separate functions:

In[]:=  f1[ x_ ] := 2 /; x <= 5
f2[ x_ ] := 10 /; x >= 5

In[]:=  p = Plot[ {f1[x], f2[x]}, {x, 0, 10}, PlotRange -> {0, 12},
DisplayFunction -> Identity ];
Out[]=  Plot::plnr:
CompiledFunction[{x}, <<1>>, <<13>>-][x]
is not a machine-size real number at x = 5.41667.

<This highly ignorable error message gets repeated a few times.>

In[]:=  g = Graphics[ {Circle[ {5, 2}, .2 ], Disk[ {5, 10}, .2 ]} ];

In[]:=  Show[ p, g, DisplayFunction -> \$DisplayFunction,
AspectRatio -> Automatic ];

Paul

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```

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