R: how to obtain specific density estimates

Question

# The Old Faithful geyser data
d <- density(faithful$eruptions, bw = "sj")
> head(d$x)
[1] 1.179869 1.188363 1.196857 1.205350 1.213844 1.222338

I'm using density function in {stats}, and I'm wondering if it's possible to see density at specific values in the output? For example, currently, I have density estimates at eruption values of [1] 1.179869 1.188363 ... but what if I want to know the density estimates at eruption values 1 2 5 10 ...? Is there a way to extract these the density object, d?

Answer 1

If I understand you correctly, you want the probabilities where the x value equals some number (3 or 4 as in my solution)?

d <- density(faithful$eruptions, bw = "sj")
densityDF <- data.frame(xVals = d$x, prob = d$y)
densityDF$xVals <- round(densityDF$xVals)

densitySearch <- densityDF[densityDF$xVals %in% c(3,4),]

Result:

   xVals       prob
157     3 0.11229482
158     3 0.10721410
159     3 0.10230912
160     3 0.09765156
161     3 0.09318662
162     3 0.08891621