eval (MATLAB Function Reference)

eval	Examples See Also

Execute a string containing a MATLAB expression

Syntax

eval(expression)
[a1,a2,a3,...] = eval(expression)
eval(expression,catch_expr)

Description

eval(expression)

executes expression, a string containing any valid MATLAB expression. You can construct expression by concatenating substrings and variables inside square brackets:

expression = [string1,int2str(var),string2,...]

[a1,a2,a3,...] = eval(expression)

executes expression and returns the results in the specified output variables. Using the eval output argument list is recommended over including the output arguments in the expression string:

eval('[a1,a2,a3,...] = function(var)')

The above syntax avoids strict checking by the MATLAB parser and can produce untrapped errors and other unexpected behavior.

eval(expression,catch_expr)

executes expression and, if an error is detected, executes the catch_expr string. If expression produces an error, the error string can be obtained with the lasterr function. This syntax is useful when expression is a string that must be constructed from substrings. If this is not the case, use the try...catch control flow statement in your code.

Examples

This example executes a simple MATLAB expression:

A = '1+4';

aval = eval(A)

aval =

     5

This for loop generates a sequence of 12 matrices named M1 through M12:

for n = 1:12

      magic_str = ['M',int2str(n),' = magic(n)'];
      eval(magic_str)

end