Using if-else statement to determine which value to input into function

Hello,

I am trying to calculate final grades from the data given in the screenshot. From left to right columns are

1) student ID

2) test 1 grade

3) test 2 grade

4) midterm grade

5) project grade

6) final grade

Tests are worth 10% and whichever test is higher is used in final calculation.

I am using the following to calculate final grades:

if samplegrades(:,2) > samplegrades(:,3)
    t = samplegrades(:,2)
else 
    t = samplegrades(:,3)
end

m = samplegrades(:,4)
p = samplegrades(:,5)
f = samplegrades(:,6)

finalgrades = @(t,m,p,f) (t.*.10+m.*.20 + p.*.20+f.*.50) 

finalgrades(t,m,p,f)

The problem is that the if-else statement doesn't seem to be using the higher t value. It is only using values from test2 to determine final grade. Please help if you can.

[dpb]

Read the doc for if, elseif, else carefully; particularly the part that explains how MATLAB determines what is TRUE.

Then see <find-array-elements-that-meet-a-condition> for introduction to logical addressing. It's possible to write the desired code w/o a for...end loop, but many beginners find that the easiest first.

Since this is a homework problem, we'll coach and let you figure out the next steps instead of just handing the solution to you...

Answer 1

[Voss]

t = max(samplegrades(:,2),samplegrades(:,3))

The if doesn't work as you expect because, when using an array condition in an if statement, the condition is considered true (so that the if-block executes) only when the condition is true for all elements of the array.

Example:

x = [1 2 3];

if x > 2 % not all elements of x are > 2
    disp('true');
else
    disp('false');
end

false

if x > 0 % all elements of x are > 0
    disp('true');
else
    disp('false');
end

true

For what you want to do in this case, you don't need an if, though. You can use max as shown above instead.

[Aayma Mughal]

Thank you so much, I was stuck for a while. :)

[Voss]

You're welcome!