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

2014 11 29
2 个回答
回答已采纳
更新时间：2014 12 6
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0 个投票

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

3 个评论
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R Bruggink
R Bruggink 2014-11-29
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.
khalid
khalid 2014-12-6
How are you doing on the new assignment?

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 采纳的回答

Image Analyst
Image Analyst 2014-11-29

0 个投票

Can you try just subtracting the min, something like
array = [structure.(field)]; % All items - no loop over ii needed.
arraySum = sum(array) - min(array);

8 个评论
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Iris
Iris 2014-11-29
how would you do it if you were storing only the data in a cell array?
Image Analyst
Image Analyst 2014-11-29
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
Iris 2014-11-29
How would you assign letter grades to arraySum?
Image Analyst
Image Analyst 2014-11-29
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
Iris 2014-11-29
编辑：Iris 2014-11-29
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
Image Analyst 2014-11-30
编辑：Image Analyst 2014-11-30
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
Mohammad Abouali 2014-12-1
编辑：Mohammad Abouali 2014-12-1
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
Iris 2014-12-5
编辑：Iris 2014-12-5
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.

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