MATLAB Function Reference

clear

Remove items from workspace, freeing up system memory

Graphical Interface

As an alternative to the clear function, use Clear Workspace in the MATLAB desktop Edit menu, or in the context menu in the Workspace browser.

Syntax

• clear
  clear name
  clear name1 name2 name3 ...
  clear global name
  clear keyword
  clear('name1','name2','name3',...)
  

Description

clear removes all variables from the workspace. This frees up system memory.

clear name removes just the M-file or MEX-file function or variable name from the workspace. You can use wildcards (*) to remove items selectively. For example, clear my* removes any variables whose names begin with the string my. It removes debugging breakpoints in M-files and reinitializes persistent variables, since the breakpoints for a function and persistent variables are cleared whenever the M-file is changed or cleared. If name is global, it is removed from the current workspace, but left accessible to any functions declaring it global. If name has been locked by mlock, it remains in memory.

Use a partial path to distinguish between different overloaded versions of a function. For example, clear inline/display clears only the display method for inline objects, leaving any other implementations in memory.

clear name1 name2 name3 ... removes name1, name2, and name3 from the workspace.

clear global name removes the global variable name. If name is global, clear name removes name from the current workspace, but leaves it accessible to any functions declaring it global. Use clear global name to completely remove a global variable.

clear keyword clears the items indicated by keyword.

Keyword	Items Cleared
all	Removes all variables, functions, and MEX-files from memory, leaving the workspace empty. Using clear all removes debugging breakpoints in M-files and reinitializes persistent variables, since the breakpoints for a function and persistent variables are cleared whenever the M-file is changed or cleared. When issued from the Command Window prompt, also removes the Java packages import list.
classes	The same as clear all, but also clears MATLAB class definitions. If any objects exist outside the workspace (for example, in user data or persistent variables in a locked M-file), a warning is issued and the class definition is not cleared. Issue a clear classes function if the number or names of fields in a class are changed.
functions	Clears all the currently compiled M-functions and MEX-functions from memory. Using clear function removes debugging breakpoints in the function M-file and reinitializes persistent variables, since the breakpoints for a function and persistent variables are cleared whenever the M-file is changed or cleared.
global	Clears all global variables from the workspace.
import	Removes the Java packages import list. It can only be issued from the Command Window prompt. It cannot be used in a function.
variables	Clears all variables from the workspace.

clear('name1','name2','name3',...) is the function form of the syntax. Use this form when the variable name or function name is stored in a string.

Remarks

When you use clear in a function, it has the following effect on items in your function and base workspaces:

• clear name--If name is the name of a function, the function is cleared in both the function workspace and in your base workspace.
• clear functions--All functions are cleared in both the function workspace and in your base workspace.
• clear global--All global variables are cleared in both the function workspace and in your base workspace.
• clear all--All functions, global variables, and classes are cleared in both the function workspace and in your base workspace.

Limitations

clear does not affect the amount of memory allocated to the MATLAB process under UNIX.

Examples

Given a workspace containing the following variables

•   Name       Size         Bytes  Class
  
    c          3x4           1200  cell array
    frame      1x1                 java.awt.Frame
    gbl1       1x1              8  double array (global)
    gbl2       1x1              8  double array (global)
    xint       1x1              1  int8 array
  

you can clear a single variable, xint, by typing

• clear xint
  

To clear all global variables, type

• clear global
  whos
    Name      Size         Bytes  Class
  
    c         3x4           1200  cell array
    frame     1x1                 java.awt.Frame
  

To clear all compiled M- and MEX-functions from memory, type clear functions. In the case shown below, clear functions was unable to clear one M-file function from memory, testfun, because the function is locked.

• clear functions           % Attempt to clear all functions.
  
  inmem
  ans = 
      'testfun'             % One M-file function remains in memory.
  
  mislocked testfun
  ans =
       1                    % This function is locked in memory.
  

Once you unlock the function from memory, you can clear it.

• munlock testfun
  clear functions
  
  inmem
  ans = 
     Empty cell array: 0-by-1
  

See Also

clc, close, import, mlock, munlock, pack, persistent, who, whos

clc

clear (serial)