How do I add the mean value to a histogram in R?
I would like to plot a histogram with mean (average) value on it (e.g. we could mark it with a blue and bold line).
I tried to do it using plot command, but even if I set the parameter add=TRUE
it didn't work.
Answer
You can use abline() to add lines to a plot:
x <- rnorm(100)
mx <- mean(x)
hist(x)
abline(v = mx, col = "blue", lwd = 2)
Have also a look at ?par for graphic parameters (like col and lwd).
In general, you can also plot lines using lines():
x <- rnorm(100, mean = 10)
mx <- mean(x)
hist(x)
lines(c(mx,mx), c(0,15), col = "red", lwd = 2)
lines(c(10, 11.5), c(0, 10), col = "steelblue", lwd = 3, lty = 22)
text(mx, 18 , round(mx, 2))
text(mx, 12 , "big", cex = 5)
where text() is used for adding text. The argument cex describes the "character expansion factor".
Also, have a look at Quick-R for an overview of basic plotting with R.