added some details about each case type of case weights

NEWS.md

@@ -1,5 +1,8 @@
 # hardhat (development version)
 
+* Added more documentation about importance and frequency weights in
+  `?importance_weights()` and `?frequency_weights()` (#214).
+
 # hardhat 1.2.0
 
 * We have reverted the change made in hardhat 1.0.0 that caused recipe

R/case-weights.R

@@ -8,6 +8,15 @@
 #' are supplied as a non-negative double vector, where fractional values are
 #' allowed.
 #'
+#' @details
+#' Importance weights focus on how much each row of the data set should
+#' influence model estimation. These can be based on data or arbitrarily set to
+#' achieve some goal.
+#'
+#' In tidymodels, importance weights only affect the model estimation and
+#' _supervised_ recipes steps. They are not used with yardstick functions for
+#' calculating measures of model performance.
+#'
 #' @param x A double vector.
 #'
 #' @return A new importance weights vector.
@@ -117,6 +126,14 @@ vec_ptype_abbr.hardhat_importance_weights <- function(x, ...) {
 #' are supplied as a non-negative integer vector, where only whole numbers are
 #' allowed.
 #'
+#' @details
+#' Frequency weights are integers that denote how many times a particular row of
+#' the data has been observed. They help compress redundant rows into a single
+#' entry.
+#'
+#' In tidymodels, frequency weights are used for all parts of the preprocessing,
+#' model fitting, and performance estimation operations.
+#'
 #' @param x An integer vector.
 #'
 #' @return A new frequency weights vector.