use options(knitr.kable.max_rows) for kable() to control the maximum …

…number of rows to be generated in the table

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 = "[email protected]", comment = c(ORCID = "0000-0003-0645-5666")),
     person("Abhraneel", "Sarma", role = "ctb"),

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
 

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