Matlab Grade book help --drop one lowest score and assigning letter grade

Hi I am building a gradebook that allows me to drop the lowest assignment score and only takes 10 assignment scores and adds all the test scores. I need to assign a letter grade to each student.

Here is some data

I am stuck on dropping the lowest score and assigning students to a grade in my function. if there is a better way of doing it without a function... please tell me...

function [sumarr] = grades(structure, field)
% FUNCTION GRADES accepts any cell array value and assigns a letter
% all data entered must be transposed from rows to colums please remember
% to transpose data example transposedata = data' ---> data = [FILE that
% was imported]

%DEFINE VARIABLES
% ii -- index variable 

ii =0 ;
array =[];
 for ii = 1:length(structure) 
     %build an array 
     array = [array structure(ii).(field)];
 end 
    % if one grade is less than 2, drop the score. 

      % assign Letter grades 

      %sum of all grades 
      sumarr = sum(array); 
  end

[R Bruggink]

How do you store your grades. like a struct: persons.torry.grade1.1 or a cell array. It makes a different when sorting the arrays.

[Iris]

I am storing them as a cell array.

[khalid]

How are you doing on the new assignment?

Answer 1

[Image Analyst]

Can you try just subtracting the min, something like

array = [structure.(field)]; % All items - no loop over ii needed.
arraySum = sum(array) - min(array);

[Iris]

how would you do it if you were storing only the data in a cell array?

[Image Analyst]

Try this:

% Create random cell array.
ca = cell(10,10);
for col = 1 : 10
  for row = 1 : 10
    ca{row, col} = randi(99, 1,1);
  end
end
% Transpose like the homework directions said
ca = ca';
celldisp(ca);
% Extract column 3, for example.
columnSum = cell2mat(ca(:,3))
theSum = sum(columnSum) - min(columnSum)

You will find it very beneficial to read this : http://matlab.wikia.com/wiki/FAQ#What_is_a_cell_array.3F

[Iris]

How would you assign letter grades to arraySum?

[Image Analyst]

What ways did you think of? You could do it several ways but probably the easiest is to use an if/elseif series to see what range the sum falls into.

[Iris]

Yeah that's how I did it.

if (arraySum >= 90 && arraySum <= 100) 
         fprintf(' final grade : %.3f\t A\n', arraySum);
  elseif (arraySum >=80 && arraySum <=89) 
     fprintf(' final grade : %.3f\t B\n', arraySum)
  elseif (arraySum >=70 && arraySum <=79) 
     fprintf(' final grade : %.3f\t B\n', arraySum)
  elseif (arraySum >=60 && arraySum <=69) 
            fprintf(' final grade : %.3f\t B\n', arraySum)
  elseif (arraySum >=0 && arraySum <=59) 
           fprintf(' final grade : %.3f\t B\n', arraySum)
  else
      printf('ERROR: invalid grade\n');
  end

[Image Analyst]

OK, good. But, Wow. You're very generous. You can get an A if you have more than 90, but if not, you'll get no worse than a B. Anyway, if you're all set and need no further advice on this topic, can you mark the answer as Accepted? Thanks in advance.

[Mohammad Abouali]

ImageAnalyst has already answered your question. Just one more note:

another way of grading without multiple if/else is this

levels=[59 69 79 89];
GradeLetter={ 'F', ... 
              'D', ...
              'C', ...
              'B', ...
              'A'};

if (arraySum<0 || arraySum >100)
  error('Imposible grade')
else
  fprintf(' final grade : %.3f\t %s\n', ...
          arraySum, ...
          GradeLetter{imquantize(arraySum,levels)} )
end

This makes it easier to change the code and add more grade levels later, such as B+, B-, A+, A-

imquantize() is part of image processing though. You need to have that toolbox.

[Iris]

I am getting issues with my statements.... since I have an array with data = [93.280 70.500 67.980 23.940 95.430 89.950 85.600 94.860 88.310 75.740 82.570 73.330 92.860 91.760 83.610 88.660 82.310 87.380 76.790 69.860 90.610 86.910 97.370 73.420 ]; I apologize for not writing this solved but I wanted to make sure I get this grade assignment right.

function gradeAssignment( arraySum )
% gradeAsssignment function takes in array 
%   Gives the data set a letter grade outprint. 

   if (arraySum >= 90.0 & arraySum <= 100.0) 
         fprintf(' final grade : %.3f\t A\n', arraySum);
  elseif (arraySum >=80.0 & arraySum <=89.0) 
        fprintf(' final grade : %.3f\t B\n', arraySum);
  elseif (arraySum >=70.0 & arraySum <=79.0) 
        fprintf(' final grade : %.3f\t B\n', arraySum);
  elseif (arraySum >=60.0 & arraySum <=69.0) 
            fprintf(' final grade : %.3f\t B\n', arraySum);
  elseif (arraySum >=0.0 & arraySum <=59.0) 
           fprintf(' final grade : %.3f\t B\n', arraySum);
   else
         fprintf('ERROR: invalid grade\n');
  end 

end

The error that I encounter is that I run through all my data and it reads everything in the array but I get ERROR:invalid input.

Answer 2

[khalid]

Do you happen to be taking this class at SMC?