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Creating a log scale in ggplot2 is a simple process that allows for displaying data with a large range of values in a more visually accurate way. To create a log scale, one must specify the “scale_y_log10” or “scale_x_log10” function within the ggplot2 code. This will transform the data into a logarithmic scale, making it easier to interpret and compare data points with a large magnitude difference. By using a log scale, the data will be evenly spaced on the axis, making it easier to identify patterns and trends. Overall, the ability to create a log scale in ggplot2 adds a valuable tool for accurately visualizing and analyzing data.
Create a Log Scale in ggplot2
Often you may want to convert the x-axis or y-axis scale of a ggplot2 plot into a log scale.
You can use one of the following two methods to do so using only ggplot2:
1. Use scale_y_continuous() or scale_x_continuous()
ggplot(df, aes(x=x, y=y)) + geom_point() + scale_y_continuous(trans='log10') + scale_x_continuous(trans='log10')
2. Use coord_trans()
ggplot(df, aes(x=x, y=y)) + geom_point() + coord_trans(y ='log10', x='log10')
If you’d like to format the axis labels to show exponents, you can use functions from the scales package:
ggplot(df, aes(x=x, y=y)) + geom_point() + scale_y_continuous(trans='log10', breaks=trans_breaks('log10', function(x) 10^x), labels=trans_format('log10', math_format(10^.x)))
This tutorial shows examples of how to use these functions in practice.
Example 1: Log Scale Using scale_y_continuous()
The following code shows how to use the scale_y_continuous() function to create a log scale for the y-axis of a scatterplot:
library(ggplot2) #create data frame df <- data.frame(x=c(2, 5, 6, 7, 9, 13, 14, 16, 18), y=c(1400, 1700, 2300, 2500, 2800, 2900, 3400, 3900, 11000)) #create scatterplot with log scale on y-axis ggplot(df, aes(x=x, y=y)) + geom_point() + scale_y_continuous(trans='log10')
Example 2: Log Scale Using coord_trans()
The following code shows how to use the coord_trans() function to create a log scale for the y-axis of a scatterplot:
library(ggplot2) #create data frame df <- data.frame(x=c(2, 5, 6, 7, 9, 13, 14, 16, 18), y=c(1400, 1700, 2300, 2500, 2800, 2900, 3400, 3900, 11000)) #create scatterplot with log scale on y-axis ggplot(df, aes(x=x, y=y)) + geom_point() + coord_trans(y='log10')
Example 3: Custom Log Scale Labels
The following code shows how to use functions from the scales package function to create a log scale for the y-axis of a scatterplot and add custom labels with exponents:
library(ggplot2) library(scales) #create data frame df <- data.frame(x=c(2, 5, 6, 7, 9, 13, 14, 16, 18), y=c(1400, 1700, 2300, 2500, 2800, 2900, 3400, 3900, 11000)) #create scatterplot with log scale on y-axis and custom labels ggplot(df, aes(x=x, y=y)) + geom_point() + scale_y_continuous(trans='log10', breaks=trans_breaks('log10', function(x) 10^x), labels=trans_format('log10', math_format(10^.x)))
Notice that the y-axis labels have exponents, unlike the previous two plots.
Additional Resources
The Complete Guide to ggplot2 Titles
A Complete Guide to the Best ggplot2 Themes
How to Create Side-by-Side Plots in ggplot2