custom ggplot2 theme

Motivation

As easy as it is to generate meaningful and complex charts with ggplot2 it can be tedious to control every detail of your chart to make it publication-ready. There are several alternative themes out there (e.g. excel style, Simpson style etc.) At Emarsys we wanted to have a theme with Emarsys colors and our own font so just using an existing theme was not enough. We spent quite of a lot of time on setting colors manually for analysis we sent to our clients. However, creating these plots were not only tedious but error-prone and they still lacked full consistency. So we looked for an easy way to modify the default ggplot2 theme.

By theme I actually mean three different components:

• color palette
• font
• theme (in ggplot2 sense, like theme_bw).

For a simple example data and base plot we will shorten our code from this:

our_ggplot + 
    scale_fill_manual(values = c("treatment" = "#377EB8",
                                 "control" = "#E41A1C")) + 
    geom_label(
        aes(label = revenue),
        position = position_dodge(width = 0.9),
        family = "Canaro Medium"
    ) + 
    theme_bw(base_family = "Canaro Medium") + 
    theme(legend.position = "bottom")

to this:

set_our_theme()
our_ggplot

Specifics

For defining a color palette we used the great ggthemr package.

get_theme_palette <- function() {

    ggthemr::define_palette(
        swatch = c("#000000",
                   "#377EB8", "#E41A1C", "#4DAF4A", "#984EA3",
                   "#FF7F00", "#FFFF33", "#A65628", "#F781BF"),
        gradient = c(lower = "#377EB8", upper = "#E41A1C")
    )
    
}

The swatch is for controlling discrete color scales (next n after first is used if n colors are needed) and the gradient is for continuous color scales. Using this theme if more discrete colors are needed than colors given will result in an error.

You can set a theme with base font size and base font family inside ggplot2, you do not need ggthemr for this.

theme_our <- function(base_size = 13) {

    theme_bw(base_size, base_family = "Canaro Medium") +
        theme(legend.position = "bottom")
        
}

However, the font family defined in a theme call won’t have effect on texts drawn by geom_text or geom_label so we have to address these separately.

update_font_defaults <- function() {

    update_geom_defaults("text", list(family = "Canaro Medium"))
    update_geom_defaults("label", list(family = "Canaro Medium"))
    
}

Now the theme setter simply calls these three functions.

set_our_theme <- function(base_size = 13)  {

    ggthemr::ggthemr(get_theme_palette())
    
    theme_set(theme_our(base_size = base_size))
    
    update_font_defaults()
    
}

set_our_theme()

## Warning: New theme missing the following elements: axis.ticks.length.x,
## axis.ticks.length.x.top, axis.ticks.length.x.bottom, axis.ticks.length.y,
## axis.ticks.length.y.left, axis.ticks.length.y.right, panel.grid, plot.tag,
## plot.tag.position

ggplot(data.table(x = as.character(1:7), y = 1), aes(x, y, fill = x)) + 
    geom_col()

ggplot(data.table(x = as.character(1:12), y = 1), aes(x, y, fill = x)) + 
    geom_col() + 
    scale_fill_hue()

ggplot(data.table(x = 1:100, y = 1), aes(x, y, fill = x)) + 
    geom_col()

ggthemr::ggthemr_reset()

our_ggplot

Conclusions

It became so easy to make our plots Emarsys-themed that now we use it by default for exploratory, internal plots as well. What we sometimes miss is an easy way to use a similar theme with plotly as well.