One or more of the arrays is categorical and either ordinal or protected

[matlab1]

question

[matlab1]

One or more of the arrays is categorical and either ordinal or protected, and the arrays do not all have the same sets of categories. Use ADDCATEGORIES to add new categories.


Categorical Arrays
Arrays of qualitative data with values from a finite set of discrete, nonnumeric data
categorical is a data type to store data with values from a finite set of discrete categories. For example, the syntax C = categorical({'R','G','B','B','G','B'}) creates a categorical array with six elements that belong to the categories R, G, or B.

A categorical array provides efficient storage and convenient manipulation of nonnumeric data, while also maintaining meaningful names for the data values. The categories can have a natural order, but it is not required.

for more information

https://www.mathworks.com/help/matlab/categorical-arrays.html





Order of Categories

categorical is a data type to store data with values from a finite set of discrete categories, which can have a natural order. You can specify and rearrange the order of categories in all categorical arrays. However, you only can treat ordinal categorical arrays as having a mathematical ordering to their categories. Use an ordinal categorical array if you want to use the functions min, max, or relational operations, such as greater than and less than.

The discrete set of pet categories {'dog' 'cat' 'bird'} has no meaningful mathematical ordering. You are free to use any category order and the meaning of the associated data does not change. For example, pets = categorical({'bird','cat','dog','dog','cat'}) creates a categorical array and the categories are listed in alphabetical order, {'bird' 'cat' 'dog'}. You can choose to specify or change the order of the categories to {'dog' 'cat' 'bird'} and the meaning of the data does not change.

ordinal categorical arrays contain categories that have a meaningful mathematical ordering. For example, the discrete set of size categories {'small', 'medium', 'large'} has the mathematical ordering small < medium < large. The first category listed is the smallest and the last category is the largest. The order of the categories in an ordinal categorical array affects the result from relational comparisons of ordinal categorical arrays.

https://www.mathworks.com/help/matlab/matlab_prog/ordinal-categorical-arrays.html