I was wondering if it is possible to plot a regression line in R including +- 2* Standard Error.
For example, with iris :
library(ggplot2)
ggplot(iris, aes(x = Petal.Length, y = Sepal.Width))+geom_smooth(method=lm, color="black")+ theme_bw()
the output is:
How would it possible (if possible) to expand the grey area for values twice the standard error?
One option to achieve your desired result would be to manually add the confidence bands via stat_smooth and making use of after_stat:
library(ggplot2)
ggplot(iris, aes(x = Petal.Length, y = Sepal.Width)) +
geom_smooth(method = lm, color = "black", se = FALSE) +
stat_smooth(aes(ymin = after_stat(y - 2 * se), ymax = after_stat(y + 2 * se)), geom = "ribbon", method = lm, fill = "grey60", alpha = .4) +
theme_bw()
#> `geom_smooth()` using formula 'y ~ x'
#> `geom_smooth()` using formula 'y ~ x'
