Check for a Legitimate Factor Object
DESCRIPTION:
Checks a factor object and returns a message of the problem encountered.
USAGE:
check.factor(x)
REQUIRED ARGUMENTS:
- x
-
an object that supposedly can be interpreted as a factor.
VALUE:
either
NULL
if there are no problems, or a character string
giving the problem encountered.
This is primarily support for various factor methods.
SEE ALSO:
.
EXAMPLES:
# this is how print.factor() uses it
if(length(xx <- check.factor(x)))
stop(paste("cannot be interpreted as a factor:\\n\\t",xx))