From aa11db848d2b736a29f64f79391e5f9d62b38f5b Mon Sep 17 00:00:00 2001
From: Yihui Xie <xie@yihui.name>
Date: Wed, 10 Apr 2024 11:09:54 -0500
Subject: [PATCH] use options(knitr.kable.max_rows) for kable() to control the
 maximum number of rows to be generated in the table

---
 DESCRIPTION  | 2 +-
 NEWS.md      | 3 +++
 R/table.R    | 5 +++++
 man/kable.Rd | 3 +++
 4 files changed, 12 insertions(+), 1 deletion(-)

diff --git a/DESCRIPTION b/DESCRIPTION
index 6bfec03e18..f7f7b4a7dd 100644
--- a/DESCRIPTION
+++ b/DESCRIPTION
@@ -1,7 +1,7 @@
 Package: knitr
 Type: Package
 Title: A General-Purpose Package for Dynamic Report Generation in R
-Version: 1.46.1
+Version: 1.46.2
 Authors@R: c(
     person("Yihui", "Xie", role = c("aut", "cre"), email = "xie@yihui.name", comment = c(ORCID = "0000-0003-0645-5666")),
     person("Abhraneel", "Sarma", role = "ctb"),
diff --git a/NEWS.md b/NEWS.md
index e40089fe1f..c5d2eba83e 100644
--- a/NEWS.md
+++ b/NEWS.md
@@ -1,5 +1,8 @@
 # CHANGES IN knitr VERSION 1.47
 
+## NEW FEATURES
+
+- For `kable()`, you can set the global option `knitr.kable.max_rows` to limit the number of rows to show in the table, e.g., `options(knitr.kable.max_rows = 30)`. This is a way to prevent `kable()` from generating a huge table from a large data object by accident.
 
 # CHANGES IN knitr VERSION 1.46
 
diff --git a/R/table.R b/R/table.R
index 820856af66..27f1ef89d5 100644
--- a/R/table.R
+++ b/R/table.R
@@ -12,6 +12,9 @@
 #' default. If you want to display them with other characters, you can set the
 #' option \code{knitr.kable.NA}, e.g. \code{options(knitr.kable.NA = '')} to
 #' hide \code{NA} values.
+#'
+#' You can set the option \code{knitr.kable.max_rows} to limit the number of
+#' rows to show in the table, e.g., \code{options(knitr.kable.max_rows = 30)}.
 #' @param x For \code{kable()}, \code{x} is an R object, which is typically a
 #'   matrix or data frame. For \code{kables()}, a list with each element being a
 #'   returned value from \code{kable()}.
@@ -123,6 +126,8 @@ kable = function(
   caption = kable_caption(label, caption, format)
 
   if (!is.matrix(x)) x = as.data.frame(x)
+  # show the maximum number of rows if set
+  if (is.numeric(nr <- getOption('knitr.kable.max_rows'))) x = head(x, nr)
   if (identical(col.names, NA)) col.names = colnames(x)
   m = ncol(x)
   # numeric columns
diff --git a/man/kable.Rd b/man/kable.Rd
index 69520598ea..dfd7fa4d2b 100644
--- a/man/kable.Rd
+++ b/man/kable.Rd
@@ -84,6 +84,9 @@ Missing values (\code{NA}) in the table are displayed as \code{NA} by
 default. If you want to display them with other characters, you can set the
 option \code{knitr.kable.NA}, e.g. \code{options(knitr.kable.NA = '')} to
 hide \code{NA} values.
+
+You can set the option \code{knitr.kable.max_rows} to limit the number of
+rows to show in the table, e.g., \code{options(knitr.kable.max_rows = 30)}.
 }
 \note{
 When using \code{kable()} as a \emph{top-level} expression, you do not