The randn function creates normally distributed random numbers.

A = randn(1,5);

Validate that the random numbers are nonnegative.

mustBeNonnegative(A)

Error using mustBeNonnegative (line 14)
Value must be nonnegative.

This class restricts the value of Prop1 to nonnegative values.

classdef MyClass
   properties
      Prop1 {mustBeNonnegative}
   end
end

Create an object and assign a value to its property.

obj = MyClass;
obj.Prop1 = -10;

Error using mustBeNonnegative (line 14)
Value must be nonnegative.

When you assign a value to the property, MATLAB calls mustBeNonnegative with the value being assigned to the property. mustBeNonnegative issues an error because the value -10 is negative.

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

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

r = mbNonnegative(-12,-4);

Error using mbNonnegative
Invalid input argument at position 2. Value must be nonnegative.