Peter Lewis Peter Lewis - 1 year ago 646
R Question

How do I change the number of decimal places on axis labels in ggplot2?

Specifically, this is in a facet_grid. Have googled extensively for similar questions but not clear on the syntax or where it goes. What I want is for every number on the y-axes to have two digits after the decimal, even if the trailing one is 0. Is this a parameter in scale_y_continuous or element_text or...?

row1 <- ggplot(sector_data[sector_data$sector %in% pages[[x]],], aes(date,price)) + geom_line() +
geom_hline(yintercept=0,size=0.3,color="gray50") +
facet_grid( ~ sector) +
scale_x_date( breaks='1 year', minor_breaks = '1 month') +
scale_y_continuous( labels = ???) +
theme(panel.grid.major.x = element_line(size=1.5),

Answer Source

In the help for ?scale_y_continuous, the argument 'labels' can be a function:

labels One of:

  • NULL for no labels

  • waiver() for the default labels computed by the transformation object

  • A character vector giving labels (must be same length as breaks)

  • A function that takes the breaks as input and returns labels as output

We will use the last option, a function that takes breaks as an argument and returns a digit with 2 decimal places.

#Our digit transformation function
scaleFUN <- function(x) sprintf("%.2f", x)

p <- ggplot(mpg, aes(displ, cty)) + geom_point()
p <- p + facet_grid(. ~ cyl)
p + scale_y_continuous(labels=scaleFUN)

enter image description here

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