Convert final grade letter into categorical array.

Question

Asad Ahmed 2021-8-10

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https://ww2.mathworks.cn/matlabcentral/answers/895997-convert-final-grade-letter-into-categorical-array

回答： Steven Lord 2021-8-10

Class_List = readcell('ClassList_2600.xls');
 N = size(Class_List);
 num_rows = N(1);
 
 
for i = 2:N
    Test = ((Class_List{i,4} + Class_List{i,5}) / 2) * 0.1;
    
    Assignment = Class_List{i,3} * 0.1;
    
    Midterm = Class_List{i,6} * 0.3;
    
    Final = Class_List{i,7} * 0.5;
    
    grade = round(Test + Assignment + Midterm + Final);
    
    if grade >= 90
        Class_List{i,8} = grade;
        Class_List{i,9} = {'A+'};
        
    elseif grade >= 80 && grade <= 89
        Class_List{i,8} = grade;
        Class_List{i,9} = {'A'};
        
    elseif grade >= 70 && grade <= 79
        Class_List{i,8} = grade;
        Class_List{i,9} = {'B'};
        
    elseif grade >= 60 && grade <= 69
        Class_List{i,8} = grade;
        Class_List{i,9} = {'C'};
        
    elseif grade >= 50 && grade <= 59
        Class_List{i,8} = grade;
        Class_List{i,9} = {'D'};
        
    elseif grade < 50
        Class_List{i,8} = grade;
        Class_List{i,9} = {'E'};
        
    end
        
end
a = Class_List(:,9);
pie = categorical(a);

So basically, I have a 26x9 cell array that shows a class list. It contains names, student ID, marks for related work, their final grade number and letter associated with it (i.e A, B, C, D, etc). I don't know how to use the categorical function. What I have above is my work.

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Answer 1

Scott MacKenzie 2021-8-10

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https://ww2.mathworks.cn/matlabcentral/answers/895997-convert-final-grade-letter-into-categorical-array#answer_764467

编辑：Scott MacKenzie 2021-8-10

在 MATLAB Online 中打开

% test data containing student letter grades

C = { 'A' 'C' 'D' 'A' 'D' 'B' 'B' 'C' 'A' };

% define C to be categorical

C = categorical(C);

% display the categories

categories(C)

ans = 4×1 cell array

{'A'} {'B'} {'C'} {'D'}

% output number of students in each letter grade category

n = countcats(C)

n = 1×4

3 2 2 2

% present in pie chart

pie(n)

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Asad Ahmed 2021-8-10

I have a question. Is it possible to use the categorical function on a column of a cell array?

Scott MacKenzie 2021-8-10

Yes

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Answer 2

Steven Lord 2021-8-10

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I would make a vector of grade numbers then use discretize to create a categorical array from that vector of grade numbers. See the "Group Data into Categorical Array" example on the documentation page for the discretize function as a model you can use.