Question

I have the following density plot:

My input data looks as follows:

PA <- c(3028.0,3083.0,2958.0,2889.0,2758.0,2815.0,2877.0,3145.0,3072.0,3056.0,2856.0,2934.0,3112.0,2913.0,2837.0)

I used the following commands to make my plot:

plot(density(PA), main="Avidin PA")
abline(v=2913, col="red")

I’ve added a reference line in red, how do I make the reference line stop when it intercepts the plot?

Answer 1

We’ll need to do a little bit of work to figure out what the density approximately is at the given x value. Once we have that we can use the lines command to plot the line of interest. This should give a start:

PA <- c(3028.0,3083.0,2958.0,2889.0,2758.0,2815.0,2877.0,3145.0,3072.0,3056.0,2856.0,2934.0,3112.0,2913.0,2837.0)

den.PA <- density(PA)
lineat = 2913

# Find which x value that the density was computed
# for is the closest to the x value we want a line at
lineheight <- den.PA$y[which.min(abs(den.PA$x - lineat))]
plot(den.PA, main="Avidin PA",)
lines(c(lineat, lineat), c(0, lineheight), col = "red")