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

[Giorgio Garziano]

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.


--
GG


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