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

*To*: mathgroup at smc.vnet.net*Subject*: [mg50019] Re: how to graphically fill the tails of a normal distribution*From*: Jens-Peer Kuska <kuska at informatik.uni-leipzig.de>*Date*: Thu, 12 Aug 2004 05:43:24 -0400 (EDT)*Organization*: Universitaet Leipzig*References*: <cfcr0h$46q$1@smc.vnet.net>*Reply-to*: kuska at informatik.uni-leipzig.de*Sender*: owner-wri-mathgroup at wolfram.com

Hi, Needs["Statistics`NormalDistribution`"] Needs["Graphics`FilledPlot`"] ndist = NormalDistribution[0, 1]; npdf = PDF[ndist, x] FilledPlot[{npdf, If[Abs[x] > 2, 0, npdf]}, {x, -4, 4}, Fills -> RGBColor[1, 0, 0], PlotRange -> All]; ?? Regards Jens Todd Allen wrote: > > 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