Re: LogPlot != Plot[Log]

*To*: mathgroup at smc.vnet.net*Subject*: [mg24299] Re: LogPlot != Plot[Log]*From*: Jens-Peer Kuska <kuska at informatik.uni-leipzig.de>*Date*: Fri, 7 Jul 2000 00:11:40 -0400 (EDT)*Organization*: Universitaet Leipzig*References*: <200006020649.CAA05402@smc.vnet.net> <8k0ugn$q5l@smc.vnet.net>*Sender*: owner-wri-mathgroup at wolfram.com

Hi, hmm - the plots are identical. But LogPlot[] uses not the natural base it uses base 10. g2 = Plot[Log[10, C1[t]] /. param, {t, 0, 2}, PlotStyle -> {RGBColor[0, 0, 1], Dashing[{0.05, 0.05}]}, PlotRange -> {{0, 2}, {Log[10, 10], Log[10, 100]}}] gives the same curve as LogPlot[]. The reason is very simple. Every semi-log paper has a base 10 scale and *not* a E scale. If anyone make a LogPlot[] he wish to have the same result as on semi-log paper. Regards Jens > Dear MathGroup, > I should like to demonstrate some transformation rules graphically using > Mathematica extended capabilities. However, the simplest example failed: > Let assume a simple exponential function with real parameters: > > C1[t_] := C0*Exp[-kel*t] > > param = {C0 -> 100, kel -> 1} > > we can plot the function easily: > > g1 = Plot[C1[t] /. param, {t, 0, 2}, PlotRange -> {{0, 2}, {10, 100}}] > > We can also make a half- logarithmic plot: > > g2 = Plot[Log[E, C1[t]] /. param, {t, 0, 2}, PlotStyle -> {RGBColor[0, 0, 1], > Dashing[{0.05, 0.05}]}, PlotRange -> {{0, 2}, {Log[10], Log[100]}}] > > In addition we can convert the y-axis to a logarithmic one: > > g3 = Show[g2, Ticks -> Join[{FullOptions[g2, Ticks][[1]], FullOptions[g2, > Ticks][[2]] /. {x_, y_Real, len_, style_} :> {x, Exp[y], len, style}}]] > > We can obtain a half-logarithmic plot by using the LogPlot function: > > << Graphics`Graphics` > > g4 = LogPlot[C1[t] /. param, {t, 0, 2}, PlotRange -> {{0, 2}, {10, 100}}] > > Now I would expect that plot g4 and g3 become identic: > > Show[{g3, g4}, PlotRange -> All] > > But it is not the case. I am sure that there is something wrong. Any help > would be appreciated. > With best regards > Gy. Csanady