Add a scatter plot to ggplot histogram

Question

I would like to add a scatter plot to overlay onto my ggplot histogram in R. On the geom_point() below it gives me an error : Error: mapping must be created by aes() Could you provide guidance ?

rand_nr <- 10000
rand_max <- 1
rand_min <- 0
lambda <- 1
x_min <- 0
x_max <- 10
bin_nr <- 50

diff_x <- (x_max - x_min) / bin_nr
edge <- seq(x_min, x_max, diff_x)
x_var <- seq(x_min, x_max, 0.01) # actual x variable
rand_var <- runif(rand_nr, rand_min, rand_max)

X <- tan(rand_var * pi / 2) # F(X)=(2/pi)*atan(x)

p <- 1 / (1 + (x_var^2))


X_df <- data.frame(X, group = "x")
P_df <- data.frame(p, group = "p")

plot(rand_var) # plot the random variables

ggplot(X_df, aes(X, probability (x),fill=group, colour=group)) + 
  geom_histogram(aes(y=..density..), breaks=edge, alpha=0.6, 
                 position="identity", lwd=0.2) +
  ggtitle("Normalized")

The working code is above. The non-working code is below

ggplot(X_df, aes(X, probability (x),fill=group, colour=group)) + 
  geom_histogram(aes(y=..density..), breaks=edge, alpha=0.6, 
                 position="identity", lwd=0.2) +
  geom_point(x_var,p,aes(x1,px1)) +
  ggtitle("Normalized") 

Answer 1

Is it what you are looking for:

ggplot(X_df, aes(x=X,fill=group, colour=group)) + 
    geom_histogram(aes(y=..density..), breaks=edge, alpha=0.6, 
             position="identity", lwd=0.2) + 
    geom_point(data=P_df,aes(x = x_var,y =p)) +
  ggtitle("Normalized") 

What has changed:

• First, since the data comes from a different dataframe, you need to add a data= argument in geom_point
• Second, as the error said, you need to provide the arguments for x and y inside of aes