How to increase error bar width using stat_summary (ggplot2) in R

March 5, 2024

I’m following this tutorial to plot a stripchart with error bars, but I’m being unable to control bar width.

# Convert the variable dose from a numeric to a factor variable
ToothGrowth$dose <- as.factor(ToothGrowth$dose)

# Plot
ggplot(data = ToothGrowth, aes(x = dose, y = len, color = dose)) +
  geom_jitter(position = position_jitter(0.2), size = 2, alpha = 0.3) +
  stat_summary(fun.data = mean_se, geom = "pointrange", size = 1.2)

When I add the argument width = 2, R returns:

Warning message:
In stat_summary(fun.data = mean_se, geom = "pointrange", size = 1.2, :
  Ignoring unknown parameters: width

How could I control the width of these error bars?

>Solution :

I think you want linewidth = 2 ?

ggplot(data = ToothGrowth, aes(x = dose, y = len, color = dose)) +
  geom_jitter(position = position_jitter(0.2), size = 2, alpha = 0.3) +
  stat_summary(fun.data = mean_se, geom = "pointrange", size = 1.2, linewidth = 2)