Determine Array Class
Query the Class Name
To determine the class of an array, use the class
function:
a = [2,5,7,11]; class(a)
ans = double
str = 'Character array';
class(str)
ans = char
Test for Array Class
The isa
function enables you to test for a specific class or a category of numeric class (numeric
, float
, integer
):
a = [2,5,7,11];
isa(a,'double')
ans = 1
Floating-point values (single and double precision values):
isa(a,'float')
ans = 1
Numeric values (floating-point and integer values):
isa(a,'numeric')
ans = 1
isa Returns True for Subclasses
isa
returns true for classes derived from the specified class. For example, the SubInt
class derives from the built-in type int16
:
classdef SubInt < int16 methods function obj = SubInt(data) if nargin == 0 data = 0; end obj = obj@int16(data); end end end
By definition, an instance of the SubInt
class is also an instance of the int16
class:
aInt = SubInt;
isa(aInt,'int16')
ans = 1
Using the integer
category also returns true
:
isa(aInt,'integer')
ans = 1
Test for Specific Types
The class
function returns the name of the most derived class of an object:
class(aInt)
ans = SubInt
Use the strcmp
function with the class
function to check for a specific class of an object:
a = int16(7);
strcmp(class(a),'int16')
ans = 1
Because the class
function returns the class name as a char
vector, the inheritance does not affect the result of the comparison performed by strcmp
:
aInt = SubInt;
strcmp(class(aInt),'int16')
ans = 0
Test for Most Derived Class
If you define functions that require inputs that are:
MATLAB® built-in types
Not subclasses of MATLAB built-in types
Use the following techniques to exclude subclasses of built-in types from the input arguments.
Test an input argument:
if strcmp(class(inputArg),'single') % Call function else inputArg = single(inputArg); end
Test for Category of Types
Suppose that you create a MEX-function, myMexFcn
, that requires two numeric inputs that must be of type double
or single
:
outArray = myMexFcn(a,b)
Define a cell array that contains the character arrays double
and single
:
floatTypes = {'double','single'};
% Test for proper types if any(strcmp(class(a),floatTypes)) && ... any(strcmp(class(b),floatTypes)) outArray = myMexFcn(a,b); else % Try to convert inputs to avoid error ... end
Another Test for Built-In Types
Use isobject
to separate built-in types from subclasses of built-in types. The isobject
function returns false
for instances of built-in types:
% Create a int16 array
a = int16([2,5,7,11]);
isobject(a)
ans = 0
Determine if an array is one of the built-in integer types:
if isa(a,'integer') && ~isobject(a) % a is a built-in integer type ... end