Dotchart / Stripchart / Dotplot GGplot stacks dots on top of each other. How can I fix this?

Question

I want to make a dotplot (stripchart) with ggplot, but the code seems to stack the dots on top of each other. There is no more variation :(. Anyone know how I can fix this?

df <- data.frame(City = c("AMS", "AMS", "AMS", "AMS", "BEL", "BEL", "BEL", "BEL"),
             Month = c(4, 5, 6, 7, 4, 5, 6, 7),
             Ratio = c(8, 9, 10, 5, 12, 13, 9, 10))

dp <- ggplot(df, aes(x = Month, y = Ratio, fill = City)) +
    geom_dotplot() 

Answer 1

Try this

dp <- ggplot(df, aes(x = Month, y = Ratio, fill = City)) +
 geom_dotplot(position = position_jitter(width = 0.1, height = 0.1)) 
dp

You may prefer position "dodge"

dp <- ggplot(df, aes(x = Month, y = Ratio, fill = City)) +
geom_dotplot(position = "dodge") 
dp

For more info see http://ggplot2.tidyverse.org/reference/position_dodge.html