learningMatlab

Debugging other people’s code

What’s wrong with the following code

Each of the following examples has one or more issues. Identify them and try to fix them. What was the intent? Why was it broken? Can you think of a better way to do it?

1. Syntax issues

   x = zeros(10,1);
   x[9] = 1; % set the 9th element to 1
   

   y = (ones(10,1), zeros(10,1)); % a long column
   

   z = Mean( rand(100,1)  );  % taking the mean
   

2. Bad intent

   v = rand(10,1); % vector of 10 random #s
   for i in 1:10
     if i == 3
     % when the index is 3 skip step by
     % setting i to 4
    i = 4;
     end
   end
   

   % calculate the mean
   nums = randn(100,1);
   mean = sum(nums)./numel(nums); % BAD! why??
   

   % calculate the variance
   nums = randn(100,1);
   var = (nums-mean(nums)).^2; % BAD for 2 reasons! why??
   

3. Bad style

   % calculate some stats
   nums = randn(100,1);
   foo = mean(nums);
   Foo = median(nums);
   foO = mode(nums);
   fOo = var(nums);
   fO0 = std(nums)./mean(nums);
   

   x = -2:0.2:2;
   y = x.^2-1+1/3-x-2.*0.2;
   

Next

Looping over plots - layer several plots together.

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