ggplot2 annotation_ticks on the outside of the plot region

Question

I try to find an elegant way to insert minor ticks on plots created with ggplot2. I found a function which does almost exactly what I want: https://rdrr.io/gith

Answer 1

Very nice functions above.

A solution I find somewhat simpler or easier to wrap my head around is to simply specify you major axis breaks in the increments you want for both major and minor breaks - so if you want major in increments of 10, and minor in increments of 5, you should nevertheless specify your major increments in steps of 5.

Then, in the theme, you are asked to give a color for the axis text. Rather than choosing one color, you can give it a list of colors - specifying whatever color you want the major axis number to be, and then NA for the minor axis color. This will give you the text on the major mark, but nothing on the 'minor' mark. Likewise, for the grid that goes inside the plot, you can specify a list for the line sizes, so that there is still a difference in thickness for major and minor gridlines within the plot, even though you are specifying the minor gridlines as major grid lines. As an example of what you could put in theme:

panel.grid.major.x = element_line(colour = c("white"), size = c(0.33, 0.2)),
panel.grid.major.y = element_line(colour = c("white"), size = c(0.33, 0.2)),
axis.text.y = element_text(colour = c("black", NA), family = "Gill Sans"),
axis.text.x = element_text(colour = c("black", NA), family = "Gill Sans"),

I suspect you can change the size of the outer tick mark in the exact same way, though I haven't tried it.