Documentation for char.trunc('datatable.prettyprint.char') (#6005)

* Documentation for char.trunc('datatable.prettyprint.char')

* small fix

* Mentioned trunc.char in 'print.data.table' function

* Improved explanation

* Update man/print.data.table.Rd

Co-authored-by: Joshua Wu <[email protected]>

* Update man/print.data.table.Rd

Co-authored-by: Joshua Wu <[email protected]>

* Update man/print.data.table.Rd

Co-authored-by: Joshua Wu <[email protected]>

* added description, deleted from alias, usage, args

* final touches

* removed name of private function

* removing space

* Final tweaks

---------

Co-authored-by: nitish jha <[email protected]>
Co-authored-by: Joshua Wu <[email protected]>
Co-authored-by: Michael Chirico <[email protected]>

man/print.data.table.Rd

@@ -13,6 +13,8 @@
   Key enhancements include automatic output compression of many observations and concise column-wise \code{class} summary.
 
   \code{format_col} and \code{format_list_item} generics provide flexibility for end-users to define custom printing methods for generic classes.
+
+  Note also the option \code{datatable.prettyprint.char}; character columns entries exceeding this limit will be truncated, with \code{...} indicating the truncation.
 }
 \usage{
   \method{print}{data.table}(x,
@@ -98,6 +100,14 @@
   print(DT, trunc.cols=TRUE)
   options(old_width)
 
+  # `char.trunc` will truncate the strings if their lengths exceed the given limit: `datatable.prettyprint.char`
+  # For example:
+
+  old = options(datatable.prettyprint.char=5L)
+  DT = data.table(x=1:2, y=c("abcdefghij", "klmnopqrstuv"))
+  DT
+  options(old)
+
   # Formatting customization
   format_col.complex = function(x, ...) sprintf('(\%.1f, \%.1fi)', Re(x), Im(x))
   x = data.table(z = c(1 + 3i, 2 - 1i, pi + 2.718i))