Table of Contents
To create a log scale in ggplot2, you first need to specify the scale_x_log10() or scale_y_log10() depending on which axis you would like to transform. Then, you must provide the name of the aesthetic mapping that you would like to transform, such as color, size, etc. Finally, you can add additional arguments to the scale, such as limits, breaks, and labels.
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.
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