Re: Question about MeshFunctions (Plot function)

• To: mathgroup at smc.vnet.net
• Subject: [mg105084] Re: Question about MeshFunctions (Plot function)
• From: dh <dh at metrohm.com>
• Date: Fri, 20 Nov 2009 06:39:51 -0500 (EST)
• References: <he36de\$ec9\$1@smc.vnet.net>

```
Vicent wrote:

> Hello.

>

> Thank you for all your answers to my previous question. They were very useful.

>

> I have a question related to the MeshFunctions option in the Plot function.

>

> I've tried this

>

>  Plot[  f[x]  ,  {x , 5 , 10}  ,  Frame -> True  ,  PlotRange -> { 2 ,

> 4 }  ,  AspectRatio -> 1/GoldenRatio  ,  PerformanceGoal -> "Quality"

> ,

>  Mesh -> { { 0. } }  ,  MeshFunctions -> { f1[#] & , f2[#] & }  ,

>  MeshStyle -> { Directive[ PointSize[ Large ] , Red ] , Directive[

> PointSize[ Large ] , Blue ] }  ]

>

> and it works OK: it plots the curve for  f[x]  and marks (in my case)

> two points on it: one red and one blue, at the points where functions

> f1[x]  and  f2[x]  take value  0.

>

> I could do the same with other different functions g[x], g1[x] and g2[x].

>

> But, is it possible to draw both curves in the same frame??  I don't

> know which is the proper syntax --I mean, this:

>

>  Plot[  { f[x] , g[x] }  ,  {x , 5 , 10}  ,  Frame -> True  ,

> PlotRange -> { 2 , 4 }  ,  AspectRatio -> 1/GoldenRatio  ,

> PerformanceGoal -> "Quality"  ,

>  Mesh -> { { 0. } }  ,  MeshFunctions -> {  { f1[#] & , f2[#] & }  , {

> g1[#] & , g2[#] & }  },

>  MeshStyle -> { Directive[ PointSize[ Large ] , Red ] , Directive[

> PointSize[ Large ] , Blue ] }  ]

>

> produces an error message. How can I get the kind of graphic I want?

>

> By the way (and this is another question, in fact), as I've just tried

> to explain, I decided to use "MeshFunctions" in order to draw a curve

> with three parts distinguished in it (the boundaries being the red and

> the blue point, I mean). I also was trying to do it with the

> "RegionFunction" option of the "Plot" sentence, but I couldn't get the

> same result (I don't want the curve to be drawn only within a given

> range, but I want the whole curve to be drawn and the different parts

> of the curve to be indicated). The different parts of the curve  f[x]

> are bounded by the zeros of the functions  f1[x]  and  f2[x],  in my

> example.

>

> Are there any other ways to get what I want??

>

> Please, if I didn't manage to explain my questions clearly enough, let

> me know. I could attach a picture of what I want to draw.

>

> Thank you in advance.

>

Hi, here is an example:

Plot[{3 + Cos[x], 3 + Sin[x]}, {x, 5, 10}, Frame -> True,

PlotRange -> {2, 4}, AspectRatio -> 1/GoldenRatio,

PerformanceGoal -> "Quality", Mesh -> {{0}},

MeshFunctions -> {#1 - 6 &, #1 - 7 &},

MeshStyle -> {Directive[PointSize[Large], Red],

Directive[PointSize[Large], Blue]}]

Daniel

```

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