Let's say I have a plot generated by this code:
library(ggplot2); ggplot(diamonds, aes(x=carat, y=price, color=cut)) + geom_point()
I would like to remove an arbitrary horizontal (or vertical) gridline, perhaps v = 12500 or v = 15000 (or both). I addition, I would like to keep the respective tickmark(s). Is there any relatively easy way to do this?
For the clarity, I do not want to get rid of all minor gridlines, especially not all the gridlines.
You can try something like this, without having to use grid to modify the underlying object.
First we get the coordinates of major/minor
ymajor = ggplot_build(p)$layout$panel_params[[1]]$y.major_source
yminor = ggplot_build(p)$layout$panel_params[[1]]$y.minor_source
yminor = setdiff(yminor,ymajor)
ymajor_cols = ifelse(ymajor == 15000,"transparent","white")
yminor_cols = ifelse(yminor == 12500,"transparent","white")
Then we add to your plot by specifying
ggplot(diamonds, aes(x=carat, y=price, color=cut)) + geom_point()+
theme(panel.grid.major.y = element_line(colour = ymajor_cols),
panel.grid.minor.y = element_line(colour = yminor_cols))
I would actually prefer specifying the major and minor breaks and specifying them in the plot, the below code gives the same results:
ymajor = c(0,5000,10000,15000)
yminor = c(0,2500,12500,17500)
ymajor_cols = ifelse(ymajor == 15000,"transparent","white")
yminor_cols = ifelse(yminor == 12500,"transparent","white")
ggplot(diamonds, aes(x=carat, y=price, color=cut)) + geom_point()+
scale_y_continuous(breaks=ymajor,minor_breaks = yminor)+
theme(panel.grid.major.y = element_line(colour = ymajor_cols),
panel.grid.minor.y = element_line(colour = yminor_cols))
