Author: Monika Huhn
Date: 2025-11-20

# Maraca Plots - Themes and Styling

#### Monika Huhn

#### 2025-11-20

In order to give the user more options in styling their plot, we have added a theme argument to the plotting functions. This vignette gives an overview over the different options.

Let us first read in some data and prepare for plotting:

    library(maraca)

    data(hce_scenario_a)

    maraca_dat <- maraca(
      data = hce_scenario_a,
      step_outcomes = c("Outcome I", "Outcome II", "Outcome III", "Outcome IV"),
      last_outcome = "Continuous outcome",
      fixed_followup_days = 3 * 365,
      column_names = c(outcome = "GROUP", arm = "TRTP", value = "AVAL0"),
      arm_levels = c(active = "Active", control = "Control"),
      compute_win_odds = TRUE
    )

## Default themes

By default, the plotting functions are using a theme called “maraca”. It is implicitly called so you do not have to specify the argument `theme = "maraca"`.

    plot(maraca_dat)

The default maraca theme adds an x- and y-axis label and angels the x-axis text for better readability. It also uses the theme “bw” of the ggplot2 package. The plot colors are not styled in the default maraca theme. We include 2 different color themes by default for the users convenience, `theme = "color1"` and `theme = "color2"`.

    plot(maraca_dat, theme = "color1")

    plot(maraca_dat, theme = "color2")

We kept the previous default styling of the maraca package as its own theme, `theme = "maraca_old"`

    plot(maraca_dat, theme = "maraca_old")

If you want to completely style your code by yourself, remove any of the extra styling with `theme = "none"`.

    plot(maraca_dat, theme = "none")

## Extending themes

The maraca plot is an ggplot2 object that can be styled by adding extra styling layers, such as any ggplot2 plot.

For example, using the `theme = "none"` styling, we can add manually the angle of the x-axis labels, remove axis texts and style with differnt colors.

    library(ggplot2)

    p <- plot(maraca_dat, theme = "none")

    p <- p +
      theme(
        legend.position = "bottom",
        axis.text.x.bottom = element_text(
          angle = 90,
          vjust = 0.5,
          hjust = 1
        ),
        axis.title.x = element_blank(),
        axis.title.y = element_blank()
      ) +
      scale_color_viridis_d(end = 0.8) +
      scale_fill_viridis_d(end = 0.8)

    p

If you want to use your own color scheme on the plots, the easiest way is to use the default styling `theme = "maraca"` and then add the colors as an extra layer.

    p <- plot(maraca_dat)

    colorScheme <- c("Active" = "steelblue", "Control" = "seagreen3")

    p <- p +
      scale_color_manual(values = colorScheme) +
      scale_fill_manual(values = colorScheme)

    p

Note that the numeric x-axis labels for the continuous endpoint part of the plot are actually text labels on the plot and cannot be directly changed using the ggplot2 `theme()` function.

The user has 2 ways of changing these labels. One is to overwrite the default text size for the plot. Do not forget to reset the default text size afterwards for further plotting.

    keep_default <- GeomLabel$default_aes$size

    # Changing default text size for the plot
    update_geom_defaults("text", list(size = 3))

    plot(maraca_dat)

    # Make sure to change defaults back to default for new plots
    update_geom_defaults("text", list(size = keep_default))

Alternatively, the user can use the parameter `continuous_grid_spacing_x` in the `plot()` function for maraca objects to create more or less grid lines and labels.

    plot(maraca_dat, continuous_grid_spacing_x = 20)