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 djmp at earthlink.net http://home.earthlink.net/~djmp/ 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 already loaded): 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