RE: Log plots: plot points *linearly* equidistant

*To*: mathgroup at smc.vnet.net*Subject*: [mg31627] RE: [mg31624] Log plots: plot points *linearly* equidistant*From*: "David Park" <djmp at earthlink.net>*Date*: Mon, 19 Nov 2001 03:11:07 -0500 (EST)*Sender*: owner-wri-mathgroup at wolfram.com

Primoz, The Log plots from Graphics`Graphics` present many difficulties in their use. The easiest approach to making log plots is to do it yourself. However, the LogScale Tick specification from Graphics`Graphics` is useful. The logstep function below allows relatively even spacing of the points on a log scale. Then you can use the regular Plot function. Needs["Graphics`Graphics`"] logstep[f_][y_] := f[10^(y)] f[x_] := UnitStep[x - 1] Plot[logstep[f][y], {y, -2, 3}, Ticks -> {LogScale, Automatic}, AxesOrigin -> {-2, 0}]; David Park djmp at earthlink.net http://home.earthlink.net/~djmp/ > From: Primoz Peterlin [mailto:primoz.peterlin at biofiz.mf.uni-lj.si] To: mathgroup at smc.vnet.net > > Hello, > > Browsing through the archives, I have seen this question coming up > recurringly at least since 1995, but with no satisfactory answer... > > The problem is that LogLinearPlot and LogLogPlot functions evaluate plot > points at values which are *linearly* equidistant on the x-axis, not > logarithmically. Why this is erroneous can be seen on a simple example: > > Needs["Graphics`Graphics`"] > LogLinearPlot[UnitStep[x - 1], {x, 0.01, 1000}] > > As far as I know, there are two ways of avoiding this behaviour: > > a) setting PlotDivision option to higher, often prohibitively high > values, > > b) evaluating one's own list of {x,} pairs and using LogLinearListPlot > or LogLog > ListPlot to plot it > > The first solution is slow and inefficient, the second one is > cumbersome. Has nobody so far been annoyed by the LogLinearPlot > behaviour enough to actually rewrite it in a decent way? :) > > With kind regards, > Primoz > > -- > Primo¾ Peterlin, In¹titut za biofiziko, Med. fakulteta, Univerza v > Ljubljani > Lipièeva 2, SI-1000 Ljubljana, Slovenija. > primoz.peterlin at biofiz.mf.uni-lj.si > Tel: +386-1-5437632, fax: +386-1-4315127, > http://sizif.mf.uni-lj.si/~peterlin/ >