Box and Whiskers/Jittered Dot Plot

Plots categorical x-axis and continuous y-axis. Inspired by Nick Cox's Stata plug-in stripplot. As per geom_boxplot, boxes reach from the first to the third quartile; whiskers extend 1.5 times the interquartile range but not beyond the most extreme data point.

stripplot(
  data,
  x,
  y,
  contrast = NULL,
  unit = NULL,
  digits = 2,
  jitter = TRUE,
  color = NULL,
  na.rm = FALSE,
  printplot = FALSE
)

Arguments

data

Data frame. Required.

x

Categorical variable for x-axis. Required.

y

Continuous variable for y-axis. Required.

contrast

If added, the mean difference between extreme categories will be added. contrast provides the preceding label. See example. Defaults to NULL (do not show contrast).

unit

Scale to print after the point estimate for the contrast between extreme categories. Defaults to NULL (no unit).

digits

Number of digits for rounding point estimate and confidence intervals of the contrast. Defaults to 2.

jitter

Avoid overplotting of points with similar values? Defaults to TRUE.

color

Variable to color data points by. Defaults to NULL (none).

na.rm

Remove "NA" category from x-axis? Defaults to FALSE.

printplot

print() the plot? Defaults to FALSE, i.e., just return the plot.

Value

ggplot object, or nothing (if plot is sent to graphics device with printplot = TRUE). Standard customization options for a ggplot object can be added on afterwards; see example.

Examples

data(mtcars)

# Basic plot
mtcars %>%
  stripplot(x = gear, y = mpg)


# Add mean difference between extreme categories, reduce digits,
# add color by 'wt', add different color scale, and label,
# all using standard ggplot syntax.
mtcars %>%
  stripplot(x = gear, y = mpg,
            contrast = "5 vs. 3 gears", unit = "mpg\n",
            digits = 1, color = wt) +
  viridis::scale_color_viridis(option = "cividis") +
  ggplot2::labs(y = "Miles per gallon", color = "Weight")