| exists(base) | R Documentation |
This function looks to see if the name x has a value bound to it.
If inherits is TRUE and a value is not found for x,
then the parent frames of envir are searched until the name
x is encountered. Warning: This is the default behaviour
for R but not for S.
If mode is specified then only objects of that mode are sought.
The function returns TRUE if the variable is encountered and
FALSE if not.
exists(x, where =NULL, envir=sys.frame(sys.parent()), frame =NULL,
mode = "any", inherits = TRUE)
x |
a variable name (given as a quoted string). |
where, envir, frame |
an environment to be searched.
By default this is the
environment where the call to envir takes place. |
mode |
the type of interest for the object. |
inherits |
should the enclosing frames of the environment be inspected. |
get.
## Define a substitute function if necessary:
if(!exists("some.fun", mode="function"))
some.fun <- function(x) { cat("some.fun(x)\n"); x }
search()
exists("ls", 2) # true even though ls is in pos=3
exists("ls", 2, inherits=F) # false