d warning and error messages show a summary of the call stack?
By default error calls are shown in non-interactive sessions.

` showNCalls ` :

    

integer. Controls how long the sequence of calls must be (in bytes) before
ellipses are used. Defaults to 40 and should be at least 30 and no more than
500.

` show.error.locations ` :

    

Should source locations of errors be printed? If set to ` TRUE ` or ` "top" `
, the source location that is highest on the stack (the most recent call) will
be printed. ` "bottom" ` will print the location of the earliest call found on
the stack.

Integer values can select other entries. The value ` 0 ` corresponds to `
"top" ` and positive values count down the stack from there. The value ` -1 `
corresponds to ` "bottom" ` and negative values count up from there.

` show.error.messages ` :

    

a logical. Should error messages be printed? Intended for use with ` [ try
](/link/try?package=base&version=3.6.2) ` or a user-installed error handler.

` stringsAsFactors ` :

    

The default setting for arguments of ` [ data.frame
](/link/data.frame?package=base&version=3.6.2) ` and ` [ read.table
](/link/read.table?package=base&version=3.6.2) ` .

` texi2dvi ` :

    

used by functions ` [ texi2dvi ](/link/texi2dvi?package=base&version=3.6.2) `
and ` [ texi2pdf ](/link/texi2pdf?package=base&version=3.6.2) ` in package
tools  .

unix-alike only:

    

Set at startup from the environment variable ` R_TEXI2DVICMD ` , which
defaults first to the value of environment variable ` TEXI2DVI ` , and then to
a value set when  R  was installed (the full path to a ` texi2dvi ` script if
one was found). If necessary, that environment variable can be set to `
"emulation" ` .

` timeout ` :

    

integer. The timeout for some Internet operations, in seconds. Default 60
seconds. See ` [ download.file
](/link/download.file?package=base&version=3.6.2) ` and ` [ connections
](/link/connections?package=base&version=3.6.2) ` .

` topLevelEnvironment ` :

    

see ` [ topenv ](/link/topenv?package=base&version=3.6.2) ` and ` [ sys.source
](/link/sys.source?package=base&version=3.6.2) ` .

` url.method ` :

    

character string: the default method for ` [ url
](/link/url?package=base&version=3.6.2) ` . Normally unset, which is
equivalent to ` "default" ` , which is ` "internal" ` except on Windows.

` useFancyQuotes ` :

    

controls the use of directional quotes in ` [ sQuote
](/link/sQuote?package=base&version=3.6.2) ` , ` dQuote ` and in rendering
text help (see ` [ Rd2txt ](/link/Rd2txt?package=base&version=3.6.2) ` in
package  tools  ). Can be ` TRUE ` , ` FALSE ` , ` "TeX" ` or ` "UTF-8" ` .

` verbose ` :

    

logical. Should  R  report extra information on progress? Set to ` TRUE ` by
the command-line option  \--verbose  .

` warn ` :

    

sets the handling of warning messages. If ` warn ` is negative all warnings
are ignored. If ` warn ` is zero (the default) warnings are stored until the
top--level function returns. If 10 or fewer warnings were signalled they will
be printed otherwise a message saying how many were signalled. An object
called ` last.warning ` is created and can be printed through the function ` [
warnings ](/link/warnings?package=base&version=3.6.2) ` . If ` warn ` is one,
warnings are printed as they occur. If ` warn ` is two (or larger, coercible
to integer), all warnings are turned into errors.

` warnPartialMatchArgs ` :

    

logical. If true, warns if partial matching is used in argument matching.

` warnPartialMatchAttr ` :

    

logical. If true, warns if partial matching is used in extracting attributes
via ` [ attr ](/link/attr?package=base&version=3.6.2) ` .

` warnPartialMatchDollar ` :

    

logical. If true, warns if partial matching is used for extraction by ` $ ` .

` warning.expression ` :

    

an  R  code expression to be called if a warning is generated, replacing the
standard message. If non-null it is called irrespective of the value of option
` warn `