Re: Plot resolution

*To*: mathgroup at smc.vnet.net*Subject*: [mg65098] Re: Plot resolution*From*: "ben" <benjamin.friedrich at gmail.com>*Date*: Tue, 14 Mar 2006 06:00:26 -0500 (EST)*References*: <dv31e3$r6d$1@smc.vnet.net>*Sender*: owner-wri-mathgroup at wolfram.com

Hi Laurentiu, Your problem is about precision: Subtracting huge numbers yielding tiny differences is always subtle. A quick'n'dirty work-around is ListPlot[Table[N[pressure, 20], {r, ro, 10^4, 10^2}],PlotJoined -> True] Here N[ ,20] simply uses more digits in the calculation. Bye Ben Laurentiu Caramete schrieb: > Hi, > > I got a problem with a plot of a function. The function 'pressure' should > decrease monotonically with r. The Plot function is giving a non-monotonic > plot at big r, this is a problem with the resolution of the plot or with the > function? How can I check that? > > \!\(Clear[r]\[IndentingNewLine] > \(ro = 10\^3;\)\[IndentingNewLine] > \(pressure = > p[r] /. \(DSolve[{D[p[r], r] == > 1\/\(\(r\^2\) \((1 + r)\)\^3\) - > Log[1 + r]\/\(\(r\^3\) \((1 + r)\)\^2\), > p[ro] == 10\^\(-7\)}, p[r], > r]\)[\([1]\)];\)\[IndentingNewLine]\[IndentingNewLine] > Plot[pressure, {r, ro, 10\^4}, PlotRange -> All]\) > > > Thanks