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. |
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.
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