warning(message)
message |
character string (of length 1) or NULL. |
warning generates a warning message that corresponds to its
argument and the expression or function from which it was called.
The result depends on the value of
options("warn").
If warn is negative warnings are ignored; if it is zero they
are stored and printed after the top–level function has completed;
if it is one they are printed as they occur and if it is 2 (or larger)
warnings are turned into errors.
If warn is zero (the default),
a top–level variable last.warning is
created. It contains the warnings which can be printed via a call to
warnings.
stop for fatal errors, warnings,
and options(warn=..).