[R] x-axis tick marks on log scale plot

[Martin Maechler]

>>>>> Brian Smith <bsmith030465 at gmail.com>
>>>>>     on Thu, 19 May 2016 11:04:55 -0400 writes:

    > Thanks all !!  On Thu, May 19, 2016 at 9:55 AM, Ivan
    > Calandra <ivan.calandra at univ-reims.fr> wrote:

    >> Hi,
    >> 
    >> You can do it by first plotting your values without the
    >> x-axis: plot(x,y,log="xy", xaxt="n")
    >> 
    >> and then plotting the x-axis with ticks where you need to:
    >> axis(side=1, at=seq(2000,8000,1000))

Getting nicer looking axis ticks  for log-scale axes (and
traditional graphics) I have created the function
   eaxis()
and utility function    pretty10exp(.)

and I also created standard R's  axTicks(.)  to help with these.

    if(!require("sfsmisc")) install.packages("sfsmisc")
    require("sfsmisc")

    x <- lseq(1e-10, 0.1, length = 201)
    plot(x, pt(x, df=3), type = "l", xaxt = "n", log = "x")
    eaxis(1)

gives the attached plot

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