Generate a documentation for datasets used in examples in an R package

Question

I am building an R package and in its documentation I included an example that uses two datasets (let's call them dataset1 and dataset2). I am now trying to write a documentation for these two datasets. To achieve this, I saved the two datasets in the "data" subfolder with names dataset1.RData and dataset2.RData using the save() function, and also created and a file named data.R in the "man" folder with the following content:

#' Title for dataset 1
#'
#' description for dataset1
#'
#' @name dataset1
#' @keywords dataset1
#' @docType data
#' @format An S4 object of class RasterLayer.
#' @details
#'     details for dataset1
#'
"dataset1"

#' Title for dataset 2
#'
#' description for dataset1
#'
#' @format An S4 object of class SpatialPolygonsDataFrame.
#' @name dataset2
#' @docType data
#' @details
#'     details for dataset2
#' \describe{
#'   \item{name_column_1}{description of column1}
#'   \item{name_column_1}{description of column1}
#' }
#'
"dataset2"

My package and the included examples check fine without any errors or warnings. However, when I run ?dataset1 or ?dataset2 I get the following message:

No documentation for ‘dataset1’ in specified packages and libraries: you could try ‘??dataset1’

I there anything I am doing wrong?