## CLEAR Clear or Delete a Variable

Section: Inspection Functions

### Usage

Clears a set of variables from the current context, or alternately, delete all variables defined in the current context. There are several formats for the function call. The first is the explicit form in which a list of variables are provided:

       clear a1 a2 ...

The variables can be persistent or global, and they will be deleted. The second form

       clear 'all'

clears all variables and libraries from the current context. Alternately, you can use the form:

       clear 'libs'

which will unload any libraries or DLLs that have been `import`ed. Optionally, you can specify that persistent variables should be cleared via:

       clear 'persistent'

and similarly for global variables:

       clear 'global'

You can use

       clear 'classes'

to clear all definitions of user-defined classes. With no arguments, `clear` defaults to clearing `'all'`.

### Example

Here is a simple example of using `clear` to delete a variable. First, we create a variable called `a`:

    --> a = 53

    a =
     53

Next, we clear `a` using the `clear` function, and verify that it is deleted.

    --> clear a
    --> a
    Error: Undefined function or variable a