Can anybody help me with the two questions below in the image? Thanks in advance

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Alaa Mohammed 2021-5-12

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编辑： Adam Danz 2021-5-19

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Adam Danz 2021-5-12

What have you tried so far?

Alaa Mohammed 2021-5-12

This is my answer for the first question, the second I can't solve it

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Answer 1

Sulaymon Eshkabilov 2021-5-13

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% Simple and easy answer here is to use logical indexing and categorical array approaches along with table, e.g.:
ID = (1:10)';
ALL=[ID, PE EM PS];  % This is your predefined/already entered table of student grades.  
EX2 = array2table(ALL,'VariableNames', {'ID', 'P_E', 'E_M', 'P_S'}); %Given data table. You can change table headers if needed.
CC = cell(size(ALL(:,2:4)));
CC(ALL(:,2:4)>90)={'A'};
CC(ALL(:,2:4)<=90 & ALL(:,2:4)>80)={'B'}
CC(ALL(:,2:4)<=80 & ALL(:,2:4)>70)={'C'}
CC(ALL(:,2:4)<=70 & ALL(:,2:4)>60)={'D'}
CC(ALL(:,2:4)<=60)={'F'}
CC = categorical(CC);
PE = CC(:,1);
EM = CC(:,2);
PS = CC(:,3);
TT = table(ID, PE, EM, PS)
Num_C = sum(CC=='C', 'all')
fprintf('# of low graded students are %d \n', Num_C)
%% Good luck

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Image Analyst 2021-5-15

For Exercise 2A, your counts of 3 for the As and Fs are correct. The exercise is missing the counts for the other grades so you need to add that in.

Alaa Mohammed 2021-5-17

OK.Thanks

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Answer 2

Image Analyst 2021-5-13

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You can either do this by doing a series of comparisons like

numCs = sum(grades > 70 & grades <= 80) % Compute the number of "C" grades.

or you can specify the edges and pass the edges into histogram() or histcounts().

You forgot to show us the way you did it, so we cannot correct your code for you.

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Answer 3

DGM 2021-5-13

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编辑：DGM 2021-5-13

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Consider this partial solution for part 2 using some simplifications based on the binning and a basic lookup table. This could be made more robust, but let's just be simple for now.

% make some random test grades
G = randi(40,10,3)+60
sn = 1:10;
examnames = {'basket weaving','daisy picking','alligator wrestling'};
lut = {'F','F','F','F','F','F','D','C','B','A'};
bin = ceil(G/10);
gradeletter = lut(bin);
table(sn',[gradeletter{:,1}]',[gradeletter{:,2}]',[gradeletter{:,3}]', ...
	'variablenames',['student id',examnames])

gives

ans =
  10×4 table
    student id    basket weaving    daisy picking    alligator wrestling
    __________    ______________    _____________    ___________________
         1              C                 D                   A         
         2              D                 B                   C         
         3              D                 C                   A         
         4              A                 B                   A         
         5              A                 C                   B         
         6              D                 A                   D         
         7              B                 A                   A         
         8              B                 A                   A         
         9              D                 A                   B         
        10              D                 D                   B         

"Find the number of students with minimum grades" sounds awfully vague do me. Does that mean "minimum passing grade" (i.e. D) or "minimum valid grade" (i.e. F)?