I found codes to calculate the sum of the area under a density curve in R. Unfortunately, I don't understand why there is always an extra ~"0.000976" at the area...
nb.data = 500000
y = rnorm(nb.data,10,2)
de = density(y)
require(zoo)
sum(diff(de$x[order(de$x)])*rollmean(de$y[order(de$x)],2))
[1] 1.000976
Why is that so?
It should be equal to 1, right?