Determine Array Class - MATLAB & Simulink (original) (raw)

Query the Class Name

To determine the class of an array, use the class function:

str = 'Character array'; class(str)

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')

Floating-point values (single and double precision values):

Numeric values (floating-point and integer values):

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')

Using the integer category also returns true:

For information on how to distinguish between built-in types and their subclasses, see Test for Subclasses of Built-in Types.

Test for Specific Types

The class function returns the name of the most derived class of an object:

Use the strcmp function with the class function to check for a specific class of an object:

a = int16(7); strcmp(class(a),'int16')

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')

Test for Subclasses of Built-in Types

The isa function returns true for subclasses of the specified class. To define functions that require inputs that are MATLAB® built-in types but exclude subclasses, use one of these techniques.

Test for Specific Types

Use strcmp and class to test for a specific built-in type. This conditional statement checks to see ifinputArg is single, and if not, it attempts to convert inputArg to single.

if strcmp(class(inputArg),'single') % Call function else inputArg = single(inputArg); end

Test for a Category of Types

Suppose that you create a MEX-function, myMexFcn, that requires two numeric inputs that must be of type double orsingle.

Define a cell array that contains the character arraysdouble and single:

floatTypes = {'double','single'};

Use strcmp and class to test the inputs against the types specified in the cell array.

if any(strcmp(class(a),floatTypes)) && ... any(strcmp(class(b),floatTypes)) outArray = myMexFcn(a,b); else % Try to convert inputs to avoid error ... end

Use isobject

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)

This conditional tests if arr is an array is one of the built-in integer types.

if isa(arr,'integer') && ~isobject(arr) % if previous statement is true, arr is a built-in integer type ... end