En snabb matlab

Reference to a cleared variable storage
Undefined function or variable 'x'

EXIST('A') returns:
      0 if A does not exist
      1 if A is a variable in the workspace
      2 if A is an M-file on MATLAB's search path.  It also returns 2 when
           A is the full pathname to a file or when A is the name of an
           ordinary file on MATLAB's search path
      3 if A is a MEX-file on MATLAB's search path
      4 if A is a MDL-file on MATLAB's search path
      5 if A is a built-in MATLAB function
      6 if A is a P-file on MATLAB's search path
      7 if A is a directory
      8 if A is a Java class