Customize Plot Appearance

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Daniel Lüdecke

2024-05-13

This vignette shows how the plots created by the sjp.* and plot_model() functions of the sjPlot package can be customized.

The examples refer to plot_grpfrq(), but most arguments are similar across all plotting function of the sjPlot package.

Tweaking plot appearance

The base function to globally change theme option for all sjp-function is set_theme(). Except for geom-colors and geom-sizes, all theme-options can be set via this function. This new theme will be applied to all following plots created with the sjPlot package.

There are various arguments to change colors, sizes, angles etc. of labels. Following example show changes to colors, sizes, angles, geom-outlines and theme.

# load libraries
library(sjPlot)  # for plotting
library(sjmisc)  # for sample data
library(ggplot2) # to access ggplot-themes

# load sample data set
data(efc)

set_theme(
  geom.outline.color = "antiquewhite4", 
  geom.outline.size = 1, 
  geom.label.size = 2,
  geom.label.color = "grey50",
  title.color = "red", 
  title.size = 1.5, 
  axis.angle.x = 45, 
  axis.textcolor = "blue", 
  base = theme_bw()
)

plot_grpfrq(
  efc$e42dep, 
  efc$e16sex, 
  title = NULL, 
  geom.colors = c("cadetblue", "coral"), 
  geom.size = 0.4
)

Using the Color Brewer palettes

All plotting functions support the usage of the Colorbrewer palettes. To apply a color brewer palette, use specify the palette as geom.colors. Any valid color brewer palette is recognized automatically.

# blank theme
set_theme(
  base = theme_blank(),
  axis.title.size = .9,
  axis.textsize = .9,
  legend.size = .7,
  legend.title.size = .8,
  geom.label.size = 3
)

plot_grpfrq(
  efc$e42dep, 
  efc$e15relat, 
  geom.colors = "PuRd", 
  show.values = FALSE
)

An overview of all supported color codes can be obtained with display.brewer.all() from the RColorBrewer package.

library(RColorBrewer)
display.brewer.all()

Plot with flipped coordinates

The plot’s axes can be flipped using coord.flip = TRUE. If needed, labels can be placed inside the bars with the vjust or hjust arguments. In such cases, you might need to adjust the label colors with geom.label.color = "white".

set_theme(geom.label.color = "white", geom.label.size = 3)

# labels appear very large due to export metrics
plot_grpfrq(efc$e42dep, efc$e16sex, coord.flip = TRUE)

Adding plot margins

Plots with no margins towards the axes may look strange to some people (not to me, though). To restore the ggplot-default behaviour, use the expand.grid argument:

plot_grpfrq(efc$e42dep, efc$e16sex, expand.grid = TRUE)

Theme options

You can use any pre-defined theme from ggplot, like theme_bw(), theme_classic() or theme_minimal() as default theme.

set_theme(base = theme_light())
plot_frq(efc$e42dep)

Pre-defined themes

There is a set of pre-defined themes from the sjPlot-package. See ?"sjPlot-themes" for a complete list.

library(sjmisc)
data(efc)
efc <- to_factor(efc, e42dep, c172code)
m <- lm(neg_c_7 ~ pos_v_4 + c12hour + e42dep + c172code, data = efc)

# reset theme
set_theme(base = theme_grey())

# forest plot of regression model
p <- plot_model(m)

# default theme
p

# pre-defined theme
p + theme_sjplot()

Pre-defined scales

There is also a new scale for ggplot-objects, scale_color_sjplot() and scale_fill_sjplot().

p + 
  theme_sjplot2() + 
  scale_color_sjplot("simply")

To see all currently available color sets, use show_sjplot_pals().

show_sjplot_pals()

Set up own themes based on existing themes

If you want to use a specific theme as base for building your own theme, use the base argument. When using base instead of theme, further arguments for settings colors etc. are not ignored.

set_theme(base = theme_bw(), axis.linecolor = "darkgreen")
plot_frq(efc$e42dep)

Further customization options

Each plotting function invisibly returns the ggplot-object. You can further add options to customize the appearance of the plot, like in the following example, where the count axis is hidden (color set to white):

set_theme(
  base = theme_classic(),
  axis.tickslen = 0, # hides tick marks
  axis.title.size = .9,
  axis.textsize = .9,
  legend.size = .7,
  legend.title.size = .8,
  geom.label.size = 3.5
)
  
plot_grpfrq(
  efc$e42dep,
  efc$e16sex,
  coord.flip = TRUE,
  show.axis.values = FALSE
) +
  theme(axis.line.x = element_line(color = "white"))

Plot legend

The plot’s legend can be customized via various legend.-arguments, see following examples:

set_theme(
  base = theme_classic(), 
  legend.title.face = "italic", # title font face
  legend.inside = TRUE,         # legend inside plot
  legend.color = "grey50",      # legend label color
  legend.pos = "bottom right",  # legend position inside plot
  axis.title.size = .9,
  axis.textsize = .9,
  legend.size = .7,
  legend.title.size = .8,
  geom.label.size = 3
)

plot_grpfrq(efc$e42dep, efc$e16sex, coord.flip = TRUE)

set_theme(
  base = theme_classic(), 
  axis.linecolor = "white",     # "remove" axis lines
  axis.textcolor.y = "darkred", # set axis label text only for y axis
  axis.tickslen = 0,            # "remove" tick marks
  legend.title.color = "red",   # legend title color
  legend.title.size = 2,        # legend title size
  legend.color = "green",       # legend label color
  legend.pos = "top",           # legend position above plot
  axis.title.size = .9,
  axis.textsize = .9,
  legend.size = .7,
  geom.label.size = 3
)

plot_grpfrq(efc$e42dep, efc$e16sex)

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