How to convert grade into letter grade

Hi guys, wonder how to transfer grade into letter grade. I have already calculated the code, which is following:

NA = 4;
PS = [75, 62, 80, 71, 0, 32, 56, 80];
PR = 68;
EM = 78;
n=2;
u=unique(PS)
if numel(u)==1 || numel(u)==2
    Result=[]
else
    Result=mean(PS(~ismember(PS,u(1:n))))
end
a = Result
if NA <= 2
    b = 15
end
if NA == 3
    b = 14
end
if NA == 4
    b = 13
end
if NA == 5
    b = 12
end
if NA == 6
    b = 11
end
if NA == 7
    b = 10
end
if NA == 8
    b = 9
end
if NA == 9
    b = 8
end
if NA == 10
    b = 7
end
if NA == 11
    b = 6
end
if NA == 12
    b = 5
end
c = PR*0.3
d = EM*0.2
e = a*0.35
grade = b + c + d + e
NA = 1;
PS = [90, 100, 100, 84, 89, 92, 73];
PR = 96;
EM = 0;
n=2; % two smallest values
u=unique(PS)
if numel(u)==1 || numel(u)==2
    Result=[]
else
    Result=mean(PS(~ismember(PS,u(1:n))))
end
a = Result
if NA <= 2
    b = 15
end
if NA == 3
    b = 14
end
if NA == 4
    b = 13
end
if NA == 5
    b = 12
end
if NA == 6
    b = 11
end
if NA == 7
    b = 10
end
if NA == 8
    b = 9
end
if NA == 9
    b = 8
end
if NA == 10
    b = 7
end
if NA == 11
    b = 6
end
if NA == 12
    b = 5
end
c = PR*0.3
d = EM*0.2
e = a*0.35
grade = b + c + d + e

I know I am super unskilled lol. Anyway, at first I tried

function grade=letter_grade
    if grade >= 91
        letter_grade='A';
    elseif n >= 81
        letter_grade='B';
    elseif n >= 71
        letter_grade='C';
    elseif n >= 61
        letter_grade='D';
    else
        letter_grade='F';
    end
end

but it doesn't work. Please help me with that, thanks in advance.

PS: 90-100 A+
       80-89  A
      70- 79 B
       60-69 C
       50-59 D
      below 50 F

Answer 1

[per isakson]

I guess this is what you intended

function  grade = letter_grade( n )
    if n >= 91
        grade='A';
    elseif n >= 81
        grade='B';
    elseif n >= 71
        grade='C';
    elseif n >= 61
        grade='D';
    else
        grade='F';
    end
end

and test the function

>> letter_grade( 75 )

which returns "C"

However, note that this function will not give results according to

PS: 90-100 A+
       80-89  A
      70- 79 B
       60-69 C
       50-59 D
      below 50 F

but it runs without errors.

[Jiawei Weng]

I have a stupid question, I should type letter_grade (75) in the command window instead of editor right?

[John D'Errico]

Yes. Use the command window. The editor is there to write and edit functions and scripts, but not to execute those functions.

[Jiawei Weng]

It is pretty weird that I put it in Command window, but it shows " Undefined function or variable 'letter_grade'." But I believe I have defined that, what am I doing wrong. Do I need to set any thing before I typr letter_grade?

[per isakson]

IMO: It is not possible to effectively use Matlab without constantly consulting the documentation. See Create Functions in Files.

"Do I need to set any thing before I typr letter_grade?" YES

1. Create a file named, letter_grade.m, that contains the code of the function
2. Save that file in a folder that is in the Matlab search path, i.e. see Search Path

[Jiawei Weng]

Great! it works perfectly, thank you so much sir.