I am having some issues calculating grades using matlab.

Hello, I am having some issues getting the program to correctly calculate grades. It works when the range of x is between 90 and 100, but anything below displays incorrectly. For the first part of the question, I cannot use elseif statements, only if. I feel that once I figure this part out, the second part where I use elseif statements will be much easier. Here is my code:

x = 80;
if x >=90;
  grade = 'A';
  if x <= 89, x >= 80;
      grade = 'B';
      if x <= 79, x >= 70;
          grade = 'C';
          if x <= 69, x >= 60;
              grade = 'D';
              if x < 60;
                  grade = 'F';
              end;
          end;
      end;
  end;
end;
disp(grade)

Any help would be very much appreciated!

Thanks, Nick

[Nicholas]

I meant to also include the error I am receiving when I enter something below 90. This is what I am seeing:

Undefined function or variable 'grade'.

Answer 1

[Jan]

At first change:

    if x <= 89, x >= 80

to:

    if x <= 89 & x >= 80

The comma evaluates the expression "x >= 80" without any effects to the previous if command.

Then check the logic again:

if x >=90
  grade = 'A';
  if x <= 89 & x >= 80

When x is greater than 90, then it cannot be between 80 and 89. So you need:

 if x >=90
    grade = 'A';
 elseif x <= 89 & x >= 80

This can be simplified: If "x >= 90" has been checked already, the test for "x <= 89" is redundant and can be omitted.

[Nicholas]

Thank you very much! The first part of the question explicitly states to not use elseif statements, but the info that you have provided me allowed me to fix my code to display correctly. Since I wasn't able to use elseif, I just ended each statement and created a new if statement for each case. Seems to work beautifully!

Thanks again,

Nick

Answer 2

[Chad Greene]

Or more succinctly,

x = 80; 

letters = {'F','D','C','B','A'}; 
disp(letters{min([ max([floor((x-50)/10) 0])+1 5])})