Plot normal distribution into existing plot

问题

I have this ggplot

ggplot(data = ph, aes(x = index1)) + geom_density()

and I would like to add a normal distribution with the same mean (= 2.71) and standard Deviation (= 0.61).

I created the normal distribution with:

nd1 <- rnorm(n = 100000, mean = 2.71), sd = 0.61)
nd1plot <- qplot(nd1, geom = "density") + theme_classic() +  ggtitle("Normalverteilung")

But now I don't know how to add it to my existing plot. Can anyone help me with this issue?

回答1:

ggplot2 has stat_function() for this kind of thing, but my solution takes a more manual approach in the name of clarity. You didn't provide an example of your data, but you should be able to replace mtcars$mpg with whatever column or vector you want.

library(tidyverse) # Gives us ggplot2 and lots of other goodies

# Choose your variable of interest
dta <- mtcars$mpg %>%
  as_tibble() # USing a tibble instead of a dataframe makes the data more predictable

# Generate normal data based on dta
norm_data <-
  rnorm(
    n = length(dta),
    mean = mean(dta$value),
    sd = sd(dta$value)
  )

# Create the plot
ggplot(dta, aes(x = value)) +
  geom_density() +
  geom_density(aes(norm_data), color = "darkgray", linetype = "dashed") +
  theme_classic()

来源：https://stackoverflow.com/questions/40868904/plot-normal-distribution-into-existing-plot