[R] Accept CSR data for predictions (#7615)

R-package/R/xgb.Booster.R

@@ -162,7 +162,11 @@ xgb.Booster.complete <- function(object, saveraw = TRUE) {
 #' Predicted values based on either xgboost model or model handle object.
 #'
 #' @param object Object of class \code{xgb.Booster} or \code{xgb.Booster.handle}
-#' @param newdata takes \code{matrix}, \code{dgCMatrix}, local data file or \code{xgb.DMatrix}.
+#' @param newdata takes \code{matrix}, \code{dgCMatrix}, \code{dgRMatrix}, \code{dsparseVector},
+#'        local data file or \code{xgb.DMatrix}.
+#'
+#'        For single-row predictions on sparse data, it's recommended to use CSR format. If passing
+#'        a sparse vector, it will take it as a row vector.
 #' @param missing Missing is only used when input is dense matrix. Pick a float value that represents
 #'        missing values in data (e.g., sometimes 0 or some other extreme value is used).
 #' @param outputmargin whether the prediction should be returned in the for of original untransformed