mustBeNegative

Validate that value is negative

Syntax

mustBeNegative(value)

Description

mustBeNegative(value) throws an error if value is not negative. A value is negative if it is less than zero. This function does not return a value.

mustBeNegative calls the lt function to determine if the input is negative. (since R2026a)

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

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 Negative

Use mustBeNegative to validate that an array contains only negative values.

Create a uniformly distributed array of random numbers.

A = rand(1,5) - 0.75;

Validate that the array elements are negative.

mustBeNegative(A)

Value must be negative.

The result of subtracting 0.75 from the array returned by rand can contain positive numbers or zeros. When a value is not negative, mustBeNegative issues an error.

Restrict Property to Negative Values

This class restricts the value of Prop1 to negative values.

classdef MyClass
   properties
      Prop1 {mustBeNegative}
   end
end

Create an object and assign a value to Prop1.

obj = MyClass;
obj.Prop1 = rand(1,5) - 0.75;

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

When you assign a value to the property, MATLAB calls mustBeNegative with the value being assigned to the property. mustBeNegative issues an error if the any of the elements in the array are not negative.

Restrict Function Argument to Negative Values

This function declares two input arguments. Input lower must be negative and input upper must not be negative.

function r = mbNegative(lower,upper)
    arguments
        lower {mustBeNegative}
        upper {mustBeNonnegative}
    end
    x = lower*pi:upper*pi;
    r = sin(x);
end

Calling the function with a value for lower that does not meet the requirements of mustBeNegative results an error.

mbNegative(0,4)

Error using mbNegative (line 3)
 mbNegative(0,4)
            ^
Invalid argument at position 1. Value must be negative.

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 lt

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

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

Version History

Introduced in R2017a

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

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

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

classdef MyClass
   properties
      Interval {mustBeNegative}
   end
end

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

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

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 mustBeNegative in the Interval property definition.

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