RE: how to graphically fill the tails of a normal distribution

• To: mathgroup at smc.vnet.net
• Subject: [mg50022] RE: [mg50012] how to graphically fill the tails of a normal distribution
• From: "David Park" <djmp at earthlink.net>
• Date: Thu, 12 Aug 2004 05:43:28 -0400 (EDT)
• Sender: owner-wri-mathgroup at wolfram.com

```Todd,

Needs["Statistics`ContinuousDistributions`"]
Needs["Graphics`FilledPlot`"]
Needs["Graphics`Graphics`"]
Needs["Graphics`Colors`"]

npdf[x_] = PDF[NormalDistribution[0, 1], x];

DisplayTogether[
FilledPlot[{0, npdf[x]}, {x, -4, -2}, Fills -> Red],
FilledPlot[{0, npdf[x]}, {x, 2, 4}, Fills -> Red],
FilledPlot[npdf[x], {x, -2, 2}, Fills -> LightBlue],
Epilog -> {Line[{{-2, 0}, {-2, npdf[-2]}}],
Line[{{2, 0}, {2, npdf[2]}}]},
PlotRange -> All,
Frame -> True,
Axes -> None,
PlotLabel -> "Normal Distribution with Filled Tails",
Background -> Linen,
ImageSize -> 450];

David Park

From: Todd Allen [mailto:genesplicer28 at yahoo.com]
To: mathgroup at smc.vnet.net

Hello all,

Hope you don't mind a question from a biologist trying to learn
Mathematica.  I have been teaching myself the syntax of Mathematica to
analyze microarray data (i.e, a technology to simultaneously monitor the
expression levels of thousands of genes).  I am interested in producing a
plot for a presentation in which the tails of a normal distribution are
colored red to illustrate a concept.  I can get the plot to work with a
single tail, but I can't get the syntax to work for both tails of the
disribution.  Here is my code:

This works for a single tail, with the following code (necessary packages
ndist=NormalDistribution[0,1]

npdf=PDF[ndist,x]

FilledPlot[{npdf,If[x³2,0,npdf]},{x,-4,4},Fills®RGBColor[1,0,0]]

However when I try the following with the Or operator (at least I think Or
operator):

FilledPlot[{npdf,If[x³2.0þx£-2.0,0,npdf]},{x,-4,4},Fills®RGBColor[1,0,0]]

I get a series of error messages:

Plot:plnr:If[x³2.0þx£-2.0,0,npdf] is not a machine-size real number at x=-4

This error repeats itself with different x values and then a normal curve is
drawn with neither tail colored in.

What am I missing here?

Any insight is much appreciated, thanks!
Todd

```

• Prev by Date: Re: x-ArcSin[Sin[x]]
• Next by Date: Re: message 50001?
• Previous by thread: Re: how to graphically fill the tails of a normal distribution
• Next by thread: raw image file