| exists {base} | R Documentation |
Search for an R object of the given name on the search path.
exists(x, where = NULL, envir = parent.frame(),
frame = NULL, mode = "any", inherits = TRUE)
x |
a variable name (given as a character string). |
where, envir, frame |
an environment to be searched. By default
this is the environment where the call to envir takes place. |
mode |
the mode of interest for the object. |
inherits |
should the enclosing frames of the environment be inspected. |
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.
The mode includes collections such as "numeric" and
"function": any member of the collection will suffice.
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=FALSE) # false