mustBePositive

Validate that value is positive

Syntax

mustBePositive(value)

Description

mustBePositive(value) throws an error if value is not positive. Values are positive when they are greater than zero. This function does not return a value.

mustBePositive calls the gt function to determine if the input is positive. (since R2026a)

Class support: All numeric classes, logical, and MATLAB^® classes that implement gt.

This function ignores input arguments that are empty values. Therefore, no error is thrown when the property or function argument value is empty.

Examples

Validate That Values Are Positive

Use mustBePositive to validate that an array contains only positive values.

Create a uniformly distributed array of random numbers.

A = rand(1,5) - 0.5;

Validate that the array elements are positive.

mustBePositive(A)

Value must be positive.

The result of subtracting 0.5 from the array returned by rand can contain negative numbers or zeros. When a value is not positive, mustBePositive issues an error.

Restrict Property to Positive Values

This class restricts the value of Prop1 to positive values.

classdef MyClass
   properties
      Prop1 {mustBePositive}
   end
end

Create an object and assign a value to its property.

obj = MyClass;
obj.Prop1 = 0;

Error setting property 'Prop1' of class 'MyClass'. Value must be positive.

When you assign a value to the property, MATLAB calls mustBePositive with the value being assigned to the property. mustBePositive issues an error because the value 0 is not positive.

Restrict Function Argument Values

This function declares two input arguments. Input A must be a numeric vector. Input ix must be a positive integer.

function r = mbPositive(A,ix)
    arguments
        A (1,:) {mustBeNumeric}
        ix {mustBePositive, mustBeInteger}
    end
    r = A(ix);
end

Calling the function with a value for ix that does not meet the requirement of mustBePositive results in an error.

A = 1:10;
ix = 0;
r = mbPositive(A,ix);

Error using mbPositive (line 4)
 r = mbPositive(A,ix);
                  ^^
Invalid argument at position 2. Value must be positive.

Input Arguments

value — Value to validate

scalar | array

Value to validate, specified as a scalar or an array of one of these types:

• logical or numeric class

• MATLAB classes that implement gt

Data Types: single | double | int8 | int16 | int32 | int64 | uint8 | uint16 | uint32 | uint64 | logical | char | string | categorical | datetime | duration | table | timetable
Complex Number Support: Yes

Tips

• mustBePositive is designed to be used for property and function argument validation.

Extended Capabilities

C/C++ Code Generation
Generate C and C++ code using MATLAB® Coder™.

GPU Code Generation
Generate CUDA® code for NVIDIA® GPUs using GPU Coder™.

GPU Arrays

Accelerate code by running on a graphics processing unit (GPU) using Parallel Computing Toolbox™.

The mustBePositive function fully supports GPU arrays. To run the function on a GPU, specify the input data as a gpuArray (Parallel Computing Toolbox). For more information, see Run MATLAB Functions on a GPU (Parallel Computing Toolbox).

Distributed Arrays

Partition large arrays across the combined memory of your cluster using Parallel Computing Toolbox™.

The mustBePositive function fully supports distributed arrays. For more information, see Run MATLAB Functions with Distributed Arrays (Parallel Computing Toolbox).

Version History

Introduced in R2017a

R2026a: mustBePositive no longer restricts input data to be real, numeric, or logical

The mustBePositive function no longer calls the isreal, isnumeric, and islogical functions to validate input. As a result, mustBePositive accepts any data type supported by the underlying comparison operator gt (or >), such as character vectors, strings, and date and time types.

For example, the Interval property definition in MyClass restricts property values using the mustBePositive validation function.

classdef MyClass
   properties
      Interval {mustBePositive}
   end
end

You can now specify the property as a value of type duration.

A = datetime("yesterday");
B = datetime("today");
s = MyClass;
s.Interval = B - A;

In previous releases, specifying the Interval property as a duration value returned this error:

Error setting property 'Interval' of class 'MyClass'. Value must be numeric or logical.

To preserve the behavior of previous releases, explicitly use mustBeReal and mustBeNumericOrLogical in your validation checks. For example, this code preserves the previous behavior of mustBePositive in the Interval property definition.

classdef MyClass
   properties
      Interval {mustBeReal,mustBeNumericOrLogical, ...
                mustBePositive}
   end
end