I need to assess agreement between to variables. The problem is that one of the variable is a continuous variable and the other is a categorical variable. I create a test that gives a certain value to a the compression of the brain. The gold standard test gives a categorical value among compressed, non compressed and partially compressed. I don´t know what test could help to probe an agreement between theses variables. I´ve been told to use a Balnd-altman plots for my purpose. What do you think?