There a several ways to avoid overplotting of labels or squeezing the plot area or to improve readability in general. Which of the proposed solutions is most suitable will depend on the lengths of the labels and the number of bars, and a number of other factors. So, you will probably have to play around.
Dummy data
Unfortunately, the OP hasn’t included a reproducible example, so we we have to make up our own data:
V1 <- c("Long label", "Longer label", "An even longer label",
"A very, very long label", "An extremely long label",
"Long, longer, longest label of all possible labels",
"Another label", "Short", "Not so short label")
df <- data.frame(V1, V2 = nchar(V1))
yaxis_label <- "A rather long axis label of character counts"
“Standard” bar chart
Labels on the x-axis are printed upright, overplotting each other:
library(ggplot2) # version 2.2.0+
p <- ggplot(df, aes(V1, V2)) + geom_col() + xlab(NULL) +
ylab(yaxis_label)
p
Note that the recently added geom_col() instead of geom_bar(stat="identity") is being used.
OP’s approach: rotate labels
Labels on x-axis are rotated by 90° degrees, squeezing the plot area:
p + theme(axis.text.x = element_text(angle = 90))
Horizontal bar chart
All labels (including the y-axis label) are printed upright, improving readability but still squeezing the plot area (but to a lesser extent as the chart is in landscape format):
p + coord_flip()
Vertical bar chart with labels wrapped
Labels are printed upright, avoiding overplotting, squeezing of plot area is reduced. You may have to play around with the width parameter to stringr::str_wrap.
q <- p + aes(stringr::str_wrap(V1, 15), V2) + xlab(NULL) +
ylab(yaxis_label)
q
Horizontal bar chart with labels wrapped
My favorite approach: All labels are printed upright, improving readability,
squeezing of plot area are is reduced. Again, you may have to play around with the width parameter to stringr::str_wrap to control the number of lines the labels are split into.
q + coord_flip()
Addendum: Abbreviate labels using scale_x_discrete()
For the sake of completeness, it should be mentioned that ggplot2 is able to abbreviate labels. In this case, I find the result disappointing.
p + scale_x_discrete(labels = abbreviate)
