diff --git a/R/data_summary.R b/R/data_summary.R
index b8f6e0ed3..bddd360ca 100644
--- a/R/data_summary.R
+++ b/R/data_summary.R
@@ -17,6 +17,8 @@
 #' as a character string, e.g. `"mean_sepal_width = mean(Sepal.Width)"`. The
 #' summary function `n()` can be used to count the number of observations.
 #'
+#' @seealso `value_at()`, which can be used inside a `data_summary()` call.
+#'
 #' @return A data frame with the requested summary statistics.
 #'
 #' @examples
@@ -42,6 +44,14 @@
 #'
 #' # count observations within groups
 #' data_summary(mtcars, observations = n(), by = c("am", "gear"))
+#'
+#' # first and last observations of "mpg" within groups
+#' data_summary(
+#'   mtcars,
+#'   first = value_at(mpg),
+#'   last = value_at(mpg, -1),
+#'   by = c("am", "gear")
+#' )
 #' @export
 data_summary <- function(x, ...) {
   UseMethod("data_summary")
diff --git a/R/value_at.R b/R/value_at.R
index 2b923b6ff..cdadc9dc6 100644
--- a/R/value_at.R
+++ b/R/value_at.R
@@ -1,8 +1,8 @@
-#' @title Find the value at a specific position in a variable
+#' @title Find the value(s) at a specific position in a variable
 #' @name value_at
 #'
-#' @description This function can be used to compute summary statistics for a
-#' data frame or a matrix.
+#' @description This function can be used to extract one or more values at a
+#' specific position in a variable.
 #'
 #' @param x A vector or factor.
 #' @param position An integer or a vector of integers, indicating the position(s)
@@ -13,6 +13,8 @@
 #' computation.
 #' @param default The value to be returned if the position is out of range.
 #'
+#' @seealso `data_summary()` to use `value_at()` inside a `data_summary()` call.
+#'
 #' @return A vector with the value(s) at the specified position(s).
 #'
 #' @examples
diff --git a/man/data_summary.Rd b/man/data_summary.Rd
index 0db624338..ba3e6cd46 100644
--- a/man/data_summary.Rd
+++ b/man/data_summary.Rd
@@ -56,4 +56,15 @@ data_summary(mtcars, "MW = mean(mpg)", "SD = sd(mpg)", by = c("am", "gear"))
 
 # count observations within groups
 data_summary(mtcars, observations = n(), by = c("am", "gear"))
+
+# first and last observations of "mpg" within groups
+data_summary(
+  mtcars,
+  first = value_at(mpg),
+  last = value_at(mpg, -1),
+  by = c("am", "gear")
+)
+}
+\seealso{
+\code{value_at()}, which can be used inside a \code{data_summary()} call.
 }
diff --git a/man/value_at.Rd b/man/value_at.Rd
index a2b1058ca..2d6c05985 100644
--- a/man/value_at.Rd
+++ b/man/value_at.Rd
@@ -2,7 +2,7 @@
 % Please edit documentation in R/value_at.R
 \name{value_at}
 \alias{value_at}
-\title{Find the value at a specific position in a variable}
+\title{Find the value(s) at a specific position in a variable}
 \usage{
 value_at(x, position = 1, default = NULL, remove_na = FALSE)
 }
@@ -23,8 +23,8 @@ computation.}
 A vector with the value(s) at the specified position(s).
 }
 \description{
-This function can be used to compute summary statistics for a
-data frame or a matrix.
+This function can be used to extract one or more values at a
+specific position in a variable.
 }
 \examples{
 data(mtcars)
@@ -37,3 +37,6 @@ value_at(mtcars$mpg, 150)
 # return 2nd and fifth value
 value_at(mtcars$mpg, c(2, 5))
 }
+\seealso{
+\code{data_summary()} to use \code{value_at()} inside a \code{data_summary()} call.
+}
diff --git a/tests/testthat/test-value_at.R b/tests/testthat/test-value_at.R
index a15256004..b6cc60a0d 100644
--- a/tests/testthat/test-value_at.R
+++ b/tests/testthat/test-value_at.R
@@ -6,4 +6,7 @@ test_that("value_at", {
   expect_equal(value_at(efc$c12hour, 5:7), efc$c12hour[5:7], ignore_attr = TRUE)
   expect_equal(value_at(efc$e42dep, 123456, default = 55), 55, ignore_attr = TRUE)
   expect_null(value_at(efc$e42dep, 123456))
+  expect_null(value_at(efc$e42dep, NULL))
+  expect_error(value_at(efc$e42dep, NA), regex = "`position` can't")
+  expect_error(value_at(efc$e42dep, c(3, NA)), regex = "`position` can't")
 })