Rotating and spacing axis labels in ggplot2

Change the last line to

q + theme(axis.text.x = element_text(angle = 90, vjust = 0.5, hjust=1))

By default, the axes are aligned at the center of the text, even when rotated. When you rotate +/- 90 degrees, you usually want it to be aligned at the edge instead:

https://learnr.files.wordpress.com/2009/03/immigration_b4.png?w=416&h=415

The image above is from this blog post.

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Use coord_flip()

data(diamonds)
diamonds$cut <- paste("Super Dee-Duper",as.character(diamonds$cut))

qplot(cut, carat, data = diamonds, geom = "boxplot") +
  coord_flip()

https://i.stack.imgur.com/kCRXo.png

Add str_wrap()

# wrap text to no more than 15 spaces
library(stringr)
diamonds$cut2 <- str_wrap(diamonds$cut, width = 15)
qplot(cut2, carat, data = diamonds, geom = "boxplot") +
  coord_flip()

https://i.stack.imgur.com/QHVDW.png

In Ch 3.9 of R for Data Science, Wickham and Grolemund speak to this exact question:

coord_flip() switches the x and y axes. This is useful (for example), if you want horizontal boxplots. It’s also useful for long labels: it’s hard to get them to fit without overlapping on the x-axis.

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ggplot 3.3.0 fixes this by providing guide_axis(angle = 90) (as guide argument to scale_.. or as x argument to guides):

library(ggplot2)
data(diamonds)
diamonds$cut <- paste("Super Dee-Duper", as.character(diamonds$cut))

ggplot(diamonds, aes(cut, carat)) +
  geom_boxplot() +
  scale_x_discrete(guide = guide_axis(angle = 90)) +
  # ... or, equivalently:
  # guides(x =  guide_axis(angle = 90)) +
  NULL

https://i.imgur.com/h7AYZOi.png

From the documentation of the angle argument:

Compared to setting the angle in theme() / element_text(), this also uses some heuristics to automatically pick the hjust and vjust that you probably want.

Alternatively, it also provides guide_axis(n.dodge = 2) (as guide argument to scale_.. or as x argument to guides) to overcome the over-plotting problem by dodging the labels vertically. It works quite well in this case:

library(ggplot2)
data(diamonds)
diamonds$cut <- paste("Super Dee-Duper",as.character(diamonds$cut))

ggplot(diamonds, aes(cut, carat)) + 
  geom_boxplot() +
  scale_x_discrete(guide = guide_axis(n.dodge = 2)) +
  NULL

https://i.imgur.com/5XmAYZk.png

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To make the text on the tick labels fully visible and read in the same direction as the y-axis label, change the last line to

q + theme(axis.text.x=element_text(angle=90, hjust=1))

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I'd like to provide an alternate solution, a robust solution similar to what I am about to propose was required in the latest version of ggtern, since introducing the canvas rotation feature.

Basically, you need to determine the relative positions using trigonometry, by building a function which returns an element_text object, given angle (ie degrees) and positioning (ie one of x,y,top or right) information.

#Load Required Libraries
library(ggplot2)
library(gridExtra)

#Build Function to Return Element Text Object
rotatedAxisElementText = function(angle,position='x'){
  angle     = angle[1]; 
  position  = position[1]
  positions = list(x=0,y=90,top=180,right=270)
  if(!position %in% names(positions))
    stop(sprintf("'position' must be one of [%s]",paste(names(positions),collapse=", ")),call.=FALSE)
  if(!is.numeric(angle))
    stop("'angle' must be numeric",call.=FALSE)
  rads  = (angle - positions[[ position ]])*pi/180
  hjust = 0.5*(1 - sin(rads))
  vjust = 0.5*(1 + cos(rads))
  element_text(angle=angle,vjust=vjust,hjust=hjust)
}

Frankly, in my opinion, I think that an 'auto' option should be made available in ggplot2 for the hjust and vjust arguments, when specifying the angle, anyway, lets demonstrate how the above works.

#Demonstrate Usage for a Variety of Rotations
df    = data.frame(x=0.5,y=0.5)
plots = lapply(seq(0,90,length.out=4),function(a){
  ggplot(df,aes(x,y)) + 
    geom_point() + 
    theme(axis.text.x = rotatedAxisElementText(a,'x'),
          axis.text.y = rotatedAxisElementText(a,'y')) +
    labs(title = sprintf("Rotated %s",a))
})
grid.arrange(grobs=plots)

Which produces the following:

https://i.stack.imgur.com/orUEV.png

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The ggpubr package offers a shortcut that does the right thing by default (right align text, middle align text box to tick):

library(ggplot2)
diamonds$cut <- paste("Super Dee-Duper", as.character(diamonds$cut))
q <- qplot(cut, carat, data = diamonds, geom = "boxplot")
q + ggpubr::rotate_x_text()

https://i.imgur.com/8oFlouO.png

^{Created on 2018-11-06 by the reprex package (v0.2.1)}

Found with a GitHub search for the relevant argument names: https://github.com/search?l=R&q=element_text+angle+90+vjust+org%3Acran&type=Code

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OUTDATED - see this answer for a simpler approach

To obtain readable x tick labels without additional dependencies, you want to use:

  ... +
  theme(axis.text.x = element_text(angle = 90, hjust = 1, vjust = 0.5)) +
  ...

This rotates the tick labels 90° counterclockwise and aligns them vertically at their end (hjust = 1) and their centers horizontally with the corresponding tick mark (vjust = 0.5).

Full example:

library(ggplot2)
data(diamonds)
diamonds$cut <- paste("Super Dee-Duper",as.character(diamonds$cut))
q <- qplot(cut,carat,data=diamonds,geom="boxplot")
q + theme(axis.text.x = element_text(angle = 90, hjust = 1, vjust = 0.5))

https://i.imgur.com/d5uCPkT.png

Note, that vertical/horizontal justification parameters vjust/hjust of element_text are relative to the text. Therefore, vjust is responsible for the horizontal alignment.

Without vjust = 0.5 it would look like this:

q + theme(axis.text.x = element_text(angle = 90, hjust = 1))

https://i.imgur.com/qUZN7kY.png

Without hjust = 1 it would look like this:

q + theme(axis.text.x = element_text(angle = 90, vjust = 0.5))

https://i.imgur.com/Wvbjn5Q.png

If for some (wired) reason you wanted to rotate the tick labels 90° clockwise (such that they can be read from the left) you would need to use: q + theme(axis.text.x = element_text(angle = -90, vjust = 0.5, hjust = -1)).

All of this has already been discussed in the comments of this answer but I come back to this question so often, that I want an answer from which I can just copy without reading the comments.

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An alternative to coord_flip() is to use the ggstance package. The advantage is that it makes it easier to combine the graphs with other graph types and you can, maybe more importantly, set fixed scale ratios for your coordinate system.

library(ggplot2)
library(ggstance)

diamonds$cut <- paste("Super Dee-Duper", as.character(diamonds$cut))

ggplot(data=diamonds, aes(carat, cut)) + geom_boxploth()

https://i.imgur.com/udGPWCg.png

^{Created on 2020-03-11 by the reprex package (v0.3.0)}

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Also with ggplot2 3.3+, we can make horizontal plots without coord_flip() as it supports bi-directional geoms, simply swapping x and y axis. https://cmdlinetips.com/2020/03/ggplot2-2-3-0-is-here-two-new-features-you-must-know/

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