[R] change the x axis tickmarks when using plot function in drc package

Giorgio Garziano giorgio.garziano at ericsson.com
Wed Dec 9 17:46:06 CET 2015

Looking at the source code of the package drc, there is something that may somehow explain what
you are experiencing:

file: plot.drc.R, function addAxes(), lines 543-626

ceilingxTicks <- ceiling(log10(xaxisTicks[-1]))
xaxisTicks <- c(xaxisTicks[1], 10^(unique(ceilingxTicks)))
xLabels <- as.character(xaxisTicks)

I may suggest two options:

1.  provide the x labels at plot() call time:

   plot(mod, type="all", log="x", xtlab = c(-2, -1, 0, 1, 2), xlab="log(dose)")

2.  try to use the option logDose in drm():

      mod <- drm(y~log(dose), fct = LL.4(), logDose=10)
      plot(mod, type="all")

Not sure if that second option fits your needs.


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