options for VectorPlot in version 7 vs VectorFieldPlot in version 6

*To*: mathgroup at smc.vnet.net*Subject*: [mg104100] options for VectorPlot in version 7 vs VectorFieldPlot in version 6*From*: janey <janemkiwi at gmail.com>*Date*: Mon, 19 Oct 2009 07:12:03 -0400 (EDT)

Dear Mathematica Usenet Group, I have been having a lot of problems with finding appropriate options in Version 7 for VectorPlot that give an acceptable, viewable plot when scales on the horizontal and vertical axes are different (I am trying to get predator prey phase portraits, plotting population of predator vs population of prey; obviously there are far more prey than predators). My only solution so far has been to put up with the complaints from using << VectorFieldPlots` about the version 6 legacy version. For example, the following works just fine (apart from annoying warnings) in version 7 given that it uses the version 6 command VectorFieldPlot in place of version 7's VectorPlot: << VectorFieldPlots`; f[x_, y_] = -.05 x + .0001 x y; g[x_, y_] = .1 y - .005 x y; field = VectorFieldPlot[{f[x, y], g[x, y]}, {x, 1, 70}, {y, 0, 2400}, PlotPoints -> {15, 15}, Frame -> True, AspectRatio -> 1] With Version 7's VectorPlot, although I can specify the number of arrows to be shown with VectorPoints replacing PlotPoints, I have not been able to set VectorScale to give me anywhere near an acceptable plot. So in version 7, f[x_, y_] = -.05 x + .0001 x y; g[x_, y_] = .1 y - .005 x y; field = VectorPlot[{f[x, y], g[x, y]}, {x, 1, 70}, {y, 0, 2400}, VectorPoints -> {15, 15}, Frame -> True, AspectRatio -> 1] looks very bad. Is there some source of information for manipulating these options somewhere besides the Mathematica Documentation Center's minimalist examples? If not, is anyone willing to share how to get success with this? Any help you can give me would be much appreciated, thanks Janey.