Using Logical Operators && and ||

Hi all,

I have a large data set that I'm trying to sort through (data is all numerical). To make things simple, I'd like to target values of variables within a certain number class.

I have 3 variables: Var1, Var2 and Var3. My goal is:

• If all three (3) variables are above 20, I would like to assign 'all_max' to another variable result.
• If any two variables - that is Var1 and Var2 or Var1 and Var 3 or Var2 and Var3, are between 20, I would like to assign 'part_max' to the variable result.

Here is a part of my MATLAB code:

if ((Var1 && Var2 && Var3)  >  20)                     % I've tried with and without the bracket in bold - doesn't give the output I'm seeking
    result = 'all_max'
elseif  (Var1 && Var2  > 20) || (Var1 && Var3  > 20) || (Var2 && Var3 > 20) 
    result = 'part_max'
else   result = 'min'
end 

I've run the above code but I'm not getting the results that I need. There's probably something wrong with my logical operators.

NB: There is more to this code including a for-loop which works perfectly. Just the problem above

Answer 1

[Guillaume]

I may sound like a broken record but I keep on saying on this forum: Don't number variables. If your variables are numbered, it's a clear indication that you should have just one variable that you index.

If you do that it makes your problem trivial to solve as well:

%instead of Var1, Var2, Var3, have a single variable Var (preferably with a more meaningful name)
%Whenever you used Var1, you now use Var(1), etc.

if all(Var > 20)
    result  = 'all_max';
elseif nnz(Var > 20) == 2  %you could use sum instead of nnz
    result = 'part_max';
else   %don't forget to end an elseif... with an else
    result = 'something_else'
end

See how much simpler the conditions are to write.

The advantage of the above is that it doesn't matter if you have 3 variables or 50,000. You can you the same code. Try writing the test for 50,000 numbered variables!

Answer 2

[Alex Mcaulley]

Try this:

if Var1>20 && Var2>20 && Var3>20                     % I've tried with and without the bracket in bold - doesn't give the output I'm seeking
    result = 'all_max'
elseif  (Var1>20 && Var2>20) || (Var1>20 && Var3>20) || (Var2>20 && Var3>20) 
    result = 'part_max'
else   result = 'min'
end