Change secondary line axis color

Question

In ggplot2, how can I modify axis.line.y only on the sec.axis (if possible)?

    p <- ggplot(mtcars, aes(cyl, mpg)) +
      geom_point()

    # Create a simple secondary axis
    p + scale_y_continuous(sec.axis = sec_axis(~.+10)) +
      theme(axis.line.y = element_line(color = "red"),
            # I can modify text color but not sure about line?
            axis.text.y.right = element_text(color = "red"))

As shown in comments below, full control over right axis elements is now comprised in the development version of ggplot2 theme( axis.line.y.right = element_line(color = "red"), axis.ticks.y.right = element_line(color = "red"))

Solution

Update:

Thanks to the comment below, this can be done by using latest dev.v of ggplot2 (Now available in the CRAN version);

install.packages("devtools")
devtools::install_github("tidyverse/ggplot2")
library(ggplot2)

p + theme( axis.line.y.right = element_line(color = "red"), 
       axis.ticks.y.right = element_line(color = "red"))

---

---

---

Maybe there is a straight solution but this is a hack/workaround that I can think of using geom_segment:

p <- ggplot(mtcars, aes(cyl, mpg)) +
     geom_point()

#get the ylim and xlim
xmin <- min(ggplot_build(p)$layout$panel_ranges[[1]]$x.range) 
xmax <- max(ggplot_build(p)$layout$panel_ranges[[1]]$x.range)
ymin <- min(ggplot_build(p)$layout$panel_ranges[[1]]$y.range)
ymax <- max(ggplot_build(p)$layout$panel_ranges[[1]]$y.range)

# Create a simple secondary axis
p + scale_y_continuous(sec.axis = sec_axis(~.+10)) +
    theme(axis.text.y.right = element_text(color = "red"))+
    geom_segment(aes(x=xmax+0.2,xend=xmax+0.2,
                     y=ymin-2,yend=ymax+2), color = "red") +
    coord_cartesian(xlim=c(xmin, xmax), ylim=c(ymin, ymax))

Comments

[M--]

+ geom_segment(aes(x=xmax+0.2,xend=xmax+0.2,y=ymin-2,yend=ymax‌​+2), color = "red") + coord_cartesian(xlim=c(xmin, xmax), ylim=c(ymin, ymax)) this would be a hack. ggplot2 is a bit hard on secondary axis and won't give you that much of flexibility. Because of this: stackoverflow.com/questions/3099219/…

[aosmith]

Based on this closed issue, I think this may be fixed in the development version of ggplot2.

[user20650]

if you update ggplot using github, this feature is no added theme( axis.line.y.right = element_line(color = "red"), axis.ticks.y.right = element_line(color = "red"))

[Lily Nature]

Hello , in this question when i run theme ( axis.line.y.right = element_line(color = "red") it says Error in (function (el, elname) : "axis.ticks.y.right" is not a valid theme element name. Why i am geeting this error, what is solution ?

[M--]

@LilyNature You need to install latest developer version from github. run this: install.packages("devtools");devtools::install_github("tidyv‌​erse/ggplot2");libra‌​ry(ggplot2) and then the code above should work for you.

[ljh2001]

@M-- Say we have another variable on the second axis called "V1." How would you change the color of that, without changing the color of other axis titles?

[M--]

@ljh2001 use this axis.title.y.right = element_text(colour = "red") within theme(...).

[tjebo]

this should now be possible with the CRAN version :)