Re: Piecewise ColorFunction

• To: mathgroup at smc.vnet.net
• Subject: [mg125660] Re: Piecewise ColorFunction
• Date: Mon, 26 Mar 2012 01:47:41 -0500 (EST)
• Delivered-to: l-mathgroup@mail-archive0.wolfram.com
• References: <jkm9sp\$bvr\$1@smc.vnet.net>

```- Try If or Which instead of Piecewise
- The function is f[x,y], not f
- You still need to tell to use Function[{x,y},  ] to associate with the
{x,y} coordinates in the plot

Like so:

Clear[f];
f[x_, y_] := If[y < 0, Green, Red];

Plot[Sin[x], {x, 0, 4 Pi}, PlotStyle -> Thick,
ColorFunction -> Function[{x, y}, f[x, y]],
ColorFunctionScaling -> False]

Plot[Sin[x], {x, 0, 4 Pi}, PlotStyle -> Thick,
ColorFunction ->
Function[{x, y},
Which[Abs[y] < 1/2, Red, y >= 1/2, Blue, y <= -1/2, Green]],
ColorFunctionScaling -> False]

University of Vermont

On 3/25/2012 1:19 AM, Hugh Goyder wrote:
> The first example below works to give a plot style with colours that vary with y-values. I then try to define a
> Piecewise function for the colour and this does not work. Am I doing something wrong? Thanks for any assistance.
>
> Plot[Sin[x], {x, 0, 4 Pi}, PlotStyle ->  Thick,
>   ColorFunction ->  Function[{x, y}, ColorData["NeonColors"][y]]]
>
>
> ClearAll[f];
> f[x_, y_] := Piecewise[{{Green, y<  0}, {Red, y>= 0}}]
>
>
> Plot[Sin[x], {x, 0, 4 Pi}, PlotStyle ->  Thick, ColorFunction ->  f]
>

--
HPR

```

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