MATLAB Function Reference    

Logical Functions
all Test to determine if all elements are nonzero
any Test for any nonzeros
exist Check if a variable or file exists
find Find indices and values of nonzero elements
is* Detect state
isa Detect an object of a given class
iskeyword Test if string is a MATLAB keyword
isvarname Test if string is a valid variable name
logical Convert numeric values to logical
mislocked True if M-file cannot be cleared

 Operators and Special Characters Language Constructs and Debugging