ggerrorbard

Building on ggplot2, the goal of ggerrorbard is to draw diagonal error bars (instead of standard vertical or horizontal error bars).

Installation

You can install the development version of ggerrorbard from GitHub like this:

# install.packages("devtools")
devtools::install_github("lmwidmayer/ggerrorbard")

Example

This is a basic example how to plot the error bars:

library("dplyr")
library("ggplot2")
library("ggerrorbard")

# rm(list = ls())
set.seed(12)

# dummy data
n <- 50
alpha.error <- 0.05

dat <- data.frame(
  x = c(
    rnorm(n, m = 8, sd = 1),
    rnorm(n, m = 8, sd = 1.75)
  ),
  y = c(
    rnorm(n, m = 4, sd = 1.5),
    rnorm(n, m = 7, sd = 1.75)
  ),
  cond = rep(c('A', 'B'), each = n)
)


# summary of data
dat$d <- with(dat, y - x) # pairwise difference of x and y
agg <- dat %>%
  group_by(cond) %>%
  summarise(x_M = mean(x),
            x_SD = sd(x),
            x_SE = sd(x) / sqrt(n()),
            y_M = mean(y),
            y_SD = sd(y),
            y_SE = sd(y) / sqrt(n()),
            d_M = mean(d),
            d_SD = sd(d),
            d_SE = sd(d) / sqrt(n()),
            n = n())

# plot
plt <- ggplot(
  data = dat,
  mapping = aes(
    x = x, y = y,
    group = cond,
    color = cond
  )
) +
  geom_abline(intercept = 0, slope = 1) +
  # observations
  geom_point(alpha = 0.3, shape = 20, size = 3) +
  # means
  geom_point(
    data = agg,
    mapping = aes(
      x = x_M, y = y_M,
      group = cond,
      color = cond
    ),
    shape = 19, size = 3
  ) +
  # errors of means
  ggerrorbard::geom_errorbard(
    data = agg,
    mapping = aes(
      x = x_M, y = y_M, # center points of error bars
      group = cond,
      color = cond,
      radius = y_SD, # radius of y error bars
      angle_deg = 0
    ),
    arrow = arrow(
      angle = 90,
      ends = "both",
      length = unit(0.025, "npc")
    ),
    linewidth = 1
  ) +
    ggerrorbard::geom_errorbard(
    data = agg,
    mapping = aes(
      x = x_M, y = y_M, # center points of error bars
      group = cond,
      color = cond,
      radius = x_SD, # radius of x error bars
      angle_deg = 90
    ),
    arrow = arrow(
      angle = 90,
      ends = "both",
      length = unit(0.025, "npc")
    ),
    linewidth = 1
  ) +
  # error of differences of means
  ggerrorbard::geom_errorbard(
    data = agg,
    mapping = aes(
      x = x_M, y = y_M, # center points of error bars
      group = cond,
      color = cond,
      radius = d_SD / 2 * sqrt(2), # radius of error bars, adjusted of 45° rotation (?)
      angle_deg = 45
    ),
    # arrows on ends of error bars
    arrow = arrow(
      angle = 90,
      ends = "both",
      length = unit(0.025, "npc")
    ),
    linewidth = 1
  ) +
  scale_x_continuous(expand = c(0, 0), limits = c(0, 12)) +
  scale_y_continuous(expand = c(0, 0), limits = c(0, 12)) +
  guides(color = guide_legend(override.aes = list(linetype = 0))) +
  coord_equal() +
  theme_minimal() +
  theme(legend.position = "top")

print(plt)

Pairwise differences. Error bars represent the standard deviations.

Use angle_deg = 0 for standard vertical error bars and angle_deg = 90 for horizontal error bars. For diagonal error bars, specify angle_deg = 45.

Limitations

• The error bars get distorted by transformations of the plotting coordinate system, e.g. coord(x = "log10", y = "log10")