%% LESSON 9: Program control
%
% *FOCUS QUESTION: How can I execute different code depending on the data?*
%

%% EXAMPLE 1: Simulate tossing a coin  (selection using |if-else|)
    toss = rand(1, 1);            % Pick a value at random between 0 and 1
    if toss <= 0.5                % Test against the value 0.5  
        fprintf('Tossed heads\n'); % Say its heads if toss is less 0.5
    else
        fprintf('Tossed tails\n'); % Say its tails if toss is less 0.5
    end;

%% EXAMPLE 2: Output the square roots of first 3 integers (simple |for| loop)
    for k = 1:3               % The loop index k takes values 1, 2, 3 
      fprintf('sqrt(%g) = %g\n', k, sqrt(k)); 
    end;


%% EXAMPLE 3: Sum the square roots of the first 10 integers (accumulation using a |for| loop ) 
    sumSqrts = 0;               % Need a variable to accumulate sum
    for k = 1:10                % Loop over the values k = 1, 2, ... 10 
      sumSqrts = sumSqrts + sqrt(k);  % Add the next sqrt root to total
    end;
    fprintf('Sum of square roots from 1 to %g is %g\n', k, sumSqrts);
   
%% EXAMPLE 4: Simulate tossing coin 50 times (|for| loop with selection and accumulation)
    numTosses = 50;            % Number of times to toss the coin
    numHeads = 0;              % Need a variable to accumulate total heads
    for k = 1:numTosses        % Loop over the values k = 1, 2, ... numTosses 
       if rand(1, 1) <= 0.5    % Add to head count if 'tossed a head' 
           numHeads = numHeads + 1;
        end;
    end;
    fprintf('%g heads in %g tosses\n', numHeads, numTosses);

%% EXAMPLE 5: Alternative implementation of coin toss simulation (vector indexing)
    timesToTosses = 50;                  % Number of times to toss the coin
    randTosses = rand(timesToTosses,1);  % Create vector of "tosses"
    numHeads = sum(randTosses <= 0.5);   % How many were heads?
    fprintf('%g heads in %g tosses\n', numHeads, numTosses); 

%% EXAMPLE 6: Load the sleep diary data 
    load diaries.mat;                        % Load the sleep diaries

%% EXAMPLE 7: Output a message if any subjects awoke after 3:30 pm 
    wakeHours = (wakeTimes - floor(wakeTimes))*24; % Calculate the wake-up hours
    lateWakeup = sum(sum(wakeHours > 15.5));       % How many late wake-ups?
    if  lateWakeup > 0                             % See if any late wake-ups
        fprintf('%g wake-ups after 3:30 pm\n', lateWakeup); 
    end;

%% EXAMPLE 8: Output subject number and gender for subjects with at least 1 wake-up after 3:30 pm
    timesLate = sum(wakeHours > 15.5);  % Times each subject woke up late
    fprintf('Subjects who had a least one wake-up after 3:30 pm:\n');
    for k = 1:length(timesLate)
        if timesLate(k) > 0
          fprintf('Subject %g: a %s with %g late wake-ups\n', ...
            k, gender{k}, timesLate(k));
        end;
    end;

%% EXAMPLE 9: Output the subject number and gender of the first student in section 3 (break) 
    sect3 = (section == 3);          % True (1) for subjects in section 3
    for k = 1:length(sect3)          % Here k = 1, 2, ... subject number
       if sect3(k)                   % If subject is in section 3
            fprintf('First subject in section 3 is a %s with subject number %g\n', ...
                gender{k}, k);
            break;                   % Get out of the loop, we done
       end;
    end;

%% EXAMPLE 10: Using |find| to perform same task as EXAMPLE 9 
    pFirst = find(section == 3, 1, 'first'); % Find position of first subject in section 3
    fprintf('First subject in section 3 is a %s with subject number %g\n', ...
                gender{pFirst}, pFirst);

%% EXAMPLE 11: Output sections that have subjects with late wake-ups (continue) 
    wakeHour = 12;                     % Wake hour to check
    averWake = mean(wakeHours);        % Compute the average wake up time for all subjects
    for s = 0:3                         % Check each section (0, 1, 2, 3)
       sectWake = averWake(section==s); % Pick out wakeups for section s
       numLate = sum(sectWake >= wakeHour);   % How many are after wakeHour?
       if numLate == 0                  % Skip this section if no late ones
           continue;
       end;
       fprintf('Section %g has %g subjects with mean wake-up after %g\n', ...
               s, numLate, wakeHour);
    end;

%% EXAMPLE 12: Output a table of early wake-ups using a loop 
    earlyWake = 6;
    fprintf('\n\n\tEarly wake-ups\n');
    fprintf('Subj\tSect\tGender\tAver Wakeup\n');    % Print out a title
    for k = 1:length(averWake)           % Here k = 1, 2, ... subject number
       if averWake(k) >= earlyWake       % Skip subjects who awoke later
           continue;
       end;
       fprintf(' %g\t  %g\t%s\t  %g\n', k, section(k), gender{k}, averWake(k));
    end;