Why am I getting a parse error at the logical operator &&?

For some reason I am getting a parse error at && which will not allow my code to run.

 function [nucleotides] = BMEactivity(m1, m2)

 for i = 1:m1(end)

 if m1(i) >= && m2(i) >= 0

    nucleotides(i) = 'A';

 elseif m1(i) < 0 && m2(i) >= 0

    nucleotides(i) = 'C';

 elseif m1(i) >= 0 && m2(i) < 0

    nucleotides = 'G';

 elseif m1(i) < 0 && m2(i) < 0

    nucleotides(i) = 'T';

 else 

 end

 end

 end

Also, I'm not quite sure if this is the correct syntax in the for loop for indexing to the last element of the array. It would be ideal if there was one expression that let me index to the end of m1 and m2 simultaneously.

Answer 1

[Star Strider]

You’re not incrementing the loop.

Try this:

m1 = randi([-1 1], 20, 1);                              % Create Data
m2 = randi([-1 1], 20, 1);                              % Create Data

for i = 1:numel(m1)

      if m1(i) >= 0 && m2(i) >= 0

          nucleotides(i) = 'A';

      elseif m1(i) < 0 && m2(i) >= 0

          nucleotides(i) = 'C';

      elseif m1(i) >= 0 && m2(i) < 0

          nucleotides(i) = 'G';

      elseif m1(i) < 0 && m2(i) < 0

          nucleotides(i) = 'T';
      end
  end

Answer 2

[Ameer Hamza]

In this line

if m1(i) >= (##) && m2(i) >= 0

You forget to write a number at (##).

[Kristen O'Mara]

Ok so that was dumb and that part works now but now it is telling me that nucleotides isn't defined. for these inputs, I need it to be giving me the string 'CCGA' and I'm nit sure where I'm going wrong.

[Steven Lord]

If you want your for loop to iterate through all the elements in m1, you don't want the upper limit to be m1(end). If m1(end) were less than 1, the body of your for loop wouldn't execute at all and so the nucleotides variable would indeed not be defined.

Use numel(m1) as the upper limit of your for loop instead. The numel function returns the NUMber of ELements in your array.

[Ameer Hamza]

Also, consider pre-allocation. For example before for loop, initialize nucleotides with zeros.

nucleotides = zeros(1, numel(m1));

[SL: fixed typo]

[Kristen O'Mara]

Thanks sm that helps!