Add documentation to corpusStats result

Change-Id: I3819d2d2b28267624d4494e16aeb84834d9198a1
diff --git a/R/KorAPCorpusStats.R b/R/KorAPCorpusStats.R
index 5acba71..fcd77df 100644
--- a/R/KorAPCorpusStats.R
+++ b/R/KorAPCorpusStats.R
@@ -34,14 +34,37 @@
 #' @param vc string describing the virtual corpus. An empty string (default) means the whole corpus, as far as it is license-wise accessible.
 #' @param verbose logical. If `TRUE`, additional diagnostics are printed.
 #' @param as.df return result as data frame instead of as S4 object?
-#' @return Object containing corpus statistics: `documents`, `tokens`, `sentences`, `paragraphs`
+#' @return Object containing corpus statistics with the following information:
+#' \describe{
+#'   \item{`vc`}{Virtual corpus definition used (empty string for entire corpus)}
+#'   \item{`documents`}{Total number of documents in the (virtual) corpus}
+#'   \item{`tokens`}{Total number of word tokens in the (virtual) corpus}
+#'   \item{`sentences`}{Total number of sentences in the (virtual) corpus}
+#'   \item{`paragraphs`}{Total number of paragraphs in the (virtual) corpus}
+#'   \item{`webUIRequestUrl`}{URL to view this corpus subset in KorAP web interface}
+#' }
+#' When `as.df=TRUE`, returns a data frame with these columns. 
+#' When `as.df=FALSE` (default), returns a KorAPCorpusStats object with these values as slots.
 #'
 #' @importFrom urltools url_encode
 #' @examples
 #' \dontrun{
-#'
+#' 
 #' kco <- KorAPConnection()
-#' corpusStats(kco, "pubDate in 2017 & textType=/Zeitung.*/")
+#' 
+#' # Get statistics for entire corpus (returns S4 object)
+#' stats <- corpusStats(kco)
+#' stats@tokens  # Access number of tokens
+#' 
+#' # Get statistics for newspaper texts from 2017 (as data frame)
+#' df <- corpusStats(kco, "pubDate in 2017 & textType=/Zeitung.*/", as.df = TRUE)
+#' df$documents  # Access number of documents
+#' 
+#' # Compare corpus sizes across years
+#' years <- 2015:2020
+#' sizes <- sapply(years, function(y) {
+#'   corpusStats(kco, paste("pubDate in", y))@tokens
+#' })
 #' }
 #'
 #' @aliases corpusStats
diff --git a/man/corpusStats-KorAPConnection-method.Rd b/man/corpusStats-KorAPConnection-method.Rd
index 31d1c87..74ba851 100644
--- a/man/corpusStats-KorAPConnection-method.Rd
+++ b/man/corpusStats-KorAPConnection-method.Rd
@@ -17,7 +17,17 @@
 \item{as.df}{return result as data frame instead of as S4 object?}
 }
 \value{
-Object containing corpus statistics: \code{documents}, \code{tokens}, \code{sentences}, \code{paragraphs}
+Object containing corpus statistics with the following information:
+\describe{
+\item{\code{vc}}{Virtual corpus definition used (empty string for entire corpus)}
+\item{\code{documents}}{Total number of documents in the (virtual) corpus}
+\item{\code{tokens}}{Total number of word tokens in the (virtual) corpus}
+\item{\code{sentences}}{Total number of sentences in the (virtual) corpus}
+\item{\code{paragraphs}}{Total number of paragraphs in the (virtual) corpus}
+\item{\code{webUIRequestUrl}}{URL to view this corpus subset in KorAP web interface}
+}
+When \code{as.df=TRUE}, returns a data frame with these columns.
+When \code{as.df=FALSE} (default), returns a KorAPCorpusStats object with these values as slots.
 }
 \description{
 Retrieve information about corpus size (documents, tokens, sentences, paragraphs)
@@ -42,7 +52,20 @@
 \dontrun{
 
 kco <- KorAPConnection()
-corpusStats(kco, "pubDate in 2017 & textType=/Zeitung.*/")
+
+# Get statistics for entire corpus (returns S4 object)
+stats <- corpusStats(kco)
+stats@tokens  # Access number of tokens
+
+# Get statistics for newspaper texts from 2017 (as data frame)
+df <- corpusStats(kco, "pubDate in 2017 & textType=/Zeitung.*/", as.df = TRUE)
+df$documents  # Access number of documents
+
+# Compare corpus sizes across years
+years <- 2015:2020
+sizes <- sapply(years, function(y) {
+  corpusStats(kco, paste("pubDate in", y))@tokens
+})
 }
 
 }