# How to 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.