Re: Plotting just specific points

• To: mathgroup at smc.vnet.net
• Subject: [mg54141] Re: [mg54043] Plotting just specific points
• From: "Wolf, Hartmut" <Hartmut.Wolf at t-systems.com>
• Date: Fri, 11 Feb 2005 03:34:33 -0500 (EST)
• Sender: owner-wri-mathgroup at wolfram.com

```>-----Original Message-----
>From: zak [mailto:chocolatez at gmail.com]
To: mathgroup at smc.vnet.net
>Sent: Wednesday, February 09, 2005 3:27 PM
>To: mathgroup at smc.vnet.net
>Subject: [mg54141] [mg54043] Plotting just specific points
>
>if i have the list:
>a={5,1,2,2,6,7,2,2,8,2}
>and in the ListPlot[a]  i want to show only the points wich
>represent only the "2" while preserving the positions of the
>"2" in the list, so i could focus my attention to a specific
>wanted values, how could i do that or even better if it is
>possible to plot the whole values of ListPlot[a] while making
>the points "2" in red color as an example.
>thanks
>zak
>
>

As for a simple example check:

In[10]:=
b = MapIndexed[If[#1 == 2, Append[#2, #1], Unevaluated[Sequence[]]] &,
a]
Out[10]=
{{3, 2}, {4, 2}, {7, 2}, {8, 2}, {10, 2}}

In[11]:=
ListPlot[a, PlotJoined -> True,
Epilog -> {Hue[0], PointSize[.02], Point /@ b}]

You may refine this on the selection criteria or formatting the points
reflecting further properties.

(Perhaps this appears to be a simpler selection:

In[12]:=
b = Cases[Transpose[{Range[Length[a]], a}], {_, 2}]
Out[12]=
{{3, 2}, {4, 2}, {7, 2}, {8, 2}, {10, 2}}

of course other variants exist)

--
Hartmut Wolf

```

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