RE: Plotting direction fields for a logistic equation

*To*: mathgroup at smc.vnet.net*Subject*: [mg37220] RE: Plotting direction fields for a logistic equation*From*: "David Park" <djmp at earthlink.net>*Date*: Thu, 17 Oct 2002 00:08:46 -0400 (EDT)*Sender*: owner-wri-mathgroup at wolfram.com

Ruben, Your plot looks bad because PlotVectorField uses AspectRatio->Automatic, which means that the t and y axes are at the same scale. This makes the plot very high and narrow. Try the following... PlotVectorField[f[t, y], {t, 0, 80}, {y, 0, 1400}, AspectRatio -> 1, Frame -> True, ImageSize -> 450]; David Park djmp at earthlink.net http://home.earthlink.net/~djmp/ From: Ruben Garcia [mailto:rubgb at yahoo.com] To: mathgroup at smc.vnet.net Hi there: I've been trying to use PlotVectorField for the following differential equation: dy/dt = 0.08*y*(1-y/1000) but I haven't been successful yet. I tried to do the following: f[t_, y_] := {1, 0.08*y*(1 - y/1000)} <<Graphics`PlotField` PlotVectorField[f[t, y], {t, 0, 80}, {y, 0, 1400}]; but I'm getting a meaningless plot so I'd appreciate if someone could tell me what is what I'm doing wrong. Thank you very much in advance, Ruben __________________________________________________ Do you Yahoo!? Faith Hill - Exclusive Performances, Videos & More http://faith.yahoo.com