无法产生R中的核密度估算器的值

Question

I'm simulating random numbers from the exponential distribution with rate=1. I have plotted a kernel density of the data using the density() function in R. What I want is a function f that gives me the value of the density at any point. I have tried the following code:

n=10^5
x=rexp(n,rate=1)
d=density(x,kernel="gaussian")
f=function(x){d$y[x]}
f(1)
plot(d)

However, f(1) clearly does not match the value of the density function at the point x=1. Where am I going wrong?

Answer 1

density produces a list which contains, in field x , the coordinates of the points at which the density is evaluated and, in field y , the estimated values of the density at these coordinates:

> str(d)
List of 7
 $ x        : num [1:512] -0.348 -0.328 -0.307 -0.286 -0.266 ...
 $ y        : num [1:512] 0.00146 0.00256 0.00435 0.00717 0.01147 ...
......

To get a function from x and y , you can use the approxfun function:

> f <- approxfun(d$x, d$y)
> f(1)
[1] 0.3665273
> dexp(1, rate=1)
[1] 0.3678794

In your code you get d$y[1] , which is the first value of d$y .