Displaying minor logarithmic ticks in x-axis in R

问题:

I have a normal distribution plot and a histogram plot with x axis in log scale displaying 0, 10^0, 10^1 ... I want to include minor ticks between the major ones. Actually I was able to change the major ticks format from 1, 2, 3 and so on to 10^0, 10^1, 10^2, 10^3 using the solution given to me in my previous question. I used the following code for the major ticks :

major.ticks <- axTicks(1) labels <- sapply(major.ticks,function(i)             as.expression(bquote(10^ .(i)))           ) axis(1,at=major.ticks,labels=labels) 

Can this be edited to just mark the minor ticks without labeling them?

回答1:

There is a function minor.tick in the package Hmisc, but that one deals poorly with logarithmical scales. I use the following function for getting minor ticks that follow the logarithmical scale. ax is the axis you use it on (same as for the function axis), n is the number of minor ticks (default to 9), t.ratio is the ratio between the major and the minor ticks, and with ... you can pass extra parameters to axis

edit : Nice idea in the comments, so I edited my function. There are two extra parameters, mn and mx for the minimum and the maximum on the logarithmic scale (mn=0 thus means the minimum is 10^0 or 1 !)

The function:

minor.ticks.axis <- function(ax,n,t.ratio=0.5,mn,mx,...){    lims <- par("usr")   if(ax %in%c(1,3)) lims <- lims[1:2] else lims[3:4]    major.ticks <- pretty(lims,n=5)   if(missing(mn)) mn <- min(major.ticks)   if(missing(mx)) mx <- max(major.ticks)    major.ticks <- major.ticks[major.ticks >= mn & major.ticks <= mx]    labels <- sapply(major.ticks,function(i)             as.expression(bquote(10^ .(i)))           )   axis(ax,at=major.ticks,labels=labels,...)    n <- n+2   minors <- log10(pretty(10^major.ticks[1:2],n))-major.ticks[1]   minors <- minors[-c(1,n)]    minor.ticks = c(outer(minors,major.ticks,`+`))   minor.ticks <- minor.ticks[minor.ticks > mn & minor.ticks < mx]     axis(ax,at=minor.ticks,tcl=par("tcl")*t.ratio,labels=FALSE) } 

This can be applied as follows :

x <- 10^(0:8) y <- 1:9 plot(log10(x),y,xaxt="n",xlab="x",xlim=c(0,9)) minor.ticks.axis(1,9,mn=0,mx=8) 

Gives :

回答2:

Here is a simple function to to this:

log10.axis <- function(side, at, ...) {     at.minor <- log10(outer(1:9, 10^(min(at):max(at))))     lab <- sapply(at, function(i) as.expression(bquote(10^ .(i))))     axis(side=side, at=at.minor, labels=NA, tcl=par("tcl")*0.5, ...)     axis(side=side, at=at, labels=lab, ...) } 

Here is an example:

x <- exp(rnorm(200, 5)) hist(log(x), 20, xaxt="n", xlim=c(0, 8)) log10.axis(1, at=seq(0, 8, 2)) 

Gives:

回答3:

Try magaxis in package magicaxis.

回答4:

Use "" for the labels of the minor ticks.

回答5:

There was a small error,

lims<-lims[3:4] was missing

   minor.ticks.axis <- function(ax,n,t.ratio=0.5,mn,mx,...){    lims <- par("usr")   if(ax %in%c(1,3)) lims <- lims[1:2] else lims <- lims[3:4]    major.ticks <- pretty(lims,n=5)   if(missing(mn)) mn <- min(major.ticks)   if(missing(mx)) mx <- max(major.ticks)    major.ticks <- major.ticks[major.ticks >= mn & major.ticks <= mx]    labels <- sapply(major.ticks,function(i)             as.expression(bquote(10^ .(i)))           )   axis(ax,at=major.ticks,labels=labels,...)    n <- n+2   minors <- log10(pretty(10^major.ticks[1:2],n))-major.ticks[1]   minors <- minors[-c(1,n)]    minor.ticks = c(outer(minors,major.ticks,`+`))   minor.ticks <- minor.ticks[minor.ticks > mn & minor.ticks < mx]     axis(ax,at=minor.ticks,tcl=par("tcl")*t.ratio,labels=FALSE) } 

回答6:

In ggplot2, we can use annotation_logticks together with scales::trans_breaks and scales::trans_format. Below is an example taken from the link above.

    library(ggplot2)      a <- ggplot(msleep, aes(bodywt, brainwt)) +       geom_point(na.rm = TRUE) +       scale_x_log10(         breaks = scales::trans_breaks("log10", function(x) 10^x),         labels = scales::trans_format("log10", scales::math_format(10^.x))       ) +       scale_y_log10(         breaks = scales::trans_breaks("log10", function(x) 10^x),         labels = scales::trans_format("log10", scales::math_format(10^.x))       ) +       theme_bw()      a + annotation_logticks() # Default: log ticks on bottom and left 

文章来源: Displaying minor logarithmic ticks in x-axis in R