Re: Piecewise ColorFunction

• To: mathgroup at smc.vnet.net
• Subject: [mg125665] Re: Piecewise ColorFunction
• From: Murray Eisenberg <murray at math.umass.edu>
• Date: Wed, 28 Mar 2012 00:32:12 -0500 (EST)
• Delivered-to: l-mathgroup@mail-archive0.wolfram.com
• References: <201203250517.AAA12261@smc.vnet.net> <201203260645.BAA21386@smc.vnet.net>
• Reply-to: murray at math.umass.edu

```Or just simply:

f[y_] = Piecewise[{{Green, y < 0}, {Red, y >= 0}}];

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

On 3/26/12 2:45 AM, Bob Hanlon wrote:
>> From the documentation: "With the usual default setting
> ColorFunctionScaling ->  True, all arguments supplied to func are
> scaled to lie in the range 0 to 1."
>
> ClearAll[f];
> f[y_] = Piecewise[{{Green, y<  0}, {Red, y>= 0}}];
>
> Plot[Sin[x], {x, 0, 4 Pi},
>   PlotStyle ->  Thick,
>   ColorFunction ->  Function[{x, y}, f[y - 1/2]]]
>
> Plot[Sin[x], {x, 0, 4 Pi},
>   PlotStyle ->  Thick,
>   ColorFunction ->  Function[{x, y}, f[y]],
>   ColorFunctionScaling ->  False]
>
> ClearAll[f];
> f = Piecewise[{{Green, #2<  0}, {Red, #2>= 0}}]&;
>
> Plot[Sin[x], {x, 0, 4 Pi},
>   PlotStyle ->  Thick,
>   ColorFunction ->  f,
>   ColorFunctionScaling ->  False]
>
>
> Bob Hanlon
>
>
> On Sun, Mar 25, 2012 at 1:17 AM, Hugh Goyder
> <h.g.d.goyder at cranfield.ac.uk>  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]
>>
>

--
Murray Eisenberg                     murray at math.umass.edu
Mathematics & Statistics Dept.
Lederle Graduate Research Tower      phone 413 549-1020 (H)
University of Massachusetts                413 545-2859 (W)
710 North Pleasant Street            fax   413 545-1801
Amherst, MA 01003-9305

```

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