function worldClock( time, shift )
%worldClock
%   Write a function called "worldClock" that creates a 1XN subplot of
%   analog clocks displaying the time of the cities. Your inputs need to be
%   a string containing the time in Atlanta, in the standard 12-hour format
%   (hh:mm), and a 1xN cell array. This 1xN cell array has 1x2 cells for
%   all of its indices. For example, if your input was 1x2, it could be:
%            { {'San Francisco', '-3:00'} , {'Austin','-1:00'} }
%   Where each index in you input cell contains a city and that city's
%   corresponding time shift from Atlanta's time.
%
%   Here are some instructions and specifications of your plot:
%   - The perimiter of the clock should be black and consist of 100 evenly 
%     spaced points using linspace()
%   - Create the circle at the center of the clock by plotting a single
%     point at (0,0) as a black circle.
%   - The length of the hour markers is .1 radially inwards from the edge
%     of the clock. That is, .1 units towards the center of the clock from
%     the edge. These will all be evenly spaced.
%   - The hour markers should be black, and correspond to the correct 
%     locations on a normal clock, where 12 o'clock is 90 degrees, and 6 
%     o'clock is 270 degrees, etc.
%   - The hour hand should point to the actual hour marker; you do not
%     need to account for how the hour hand would shift based on the minute
%     time in a real clock.
%   - The length of the hour hand should be .6 units.
%   - The length of the minute hand should be .9 units.
%   - The hour hand should be blue.
%   - The minute hand should be red.
%   - The title of each plot should be the city.
%   - The axis should be square and turned off.
%   - The subplot should have the same dimensions as the input cell array,
%     with each city and time appearing in the same order as they did in
%     the cell array.
%
% Hints:
%  - Keep in mind that the sin() and cos() functions take in radians
%  - Whether a time is AM/PM will not matter, but your times are still on a
%    12 hour scale. As in: if Atlanta's time is 11:00, a shift of +2:00
%    will yield a time of 1:00, but it will not matter which of these is AM
%    or PM. You do not need to keep track of this. Shifts of greater than
%    12 hours are possible.
%  - The rotation matrix could be useful for parts of this problem.
numClocks = length(shift);

for ndx = 1:numClocks
    subplot(1, numClocks, ndx);
    th = linspace(0, 2*pi, 100);
    plot(cos(th), sin(th), 'k-');
    hold on
    plot(0, 0, 'ko');
    hrmark = linspace(0, 2*pi, 13);
    hrmark = hrmark(end:-1:1);
    for i = 1:13
        plot([(0.9*cos(hrmark(i))), (1*cos(hrmark(i)))], ...
             [(0.9*sin(hrmark(i))), (1*sin(hrmark(i)))], 'k');
    end

    [atlhr, minutes] = strtok(time, ':');
    atlhr = str2num(atlhr) - 1;
    [hr, ~] = strtok(shift{ndx}{2}, ':');
    hrshift = hr(1);
    hr = str2num(hr(2:end));
    if hr >= 12
        hr = mod(hr, 12);
    end
    if hrshift == '+'
        hr = atlhr - hr;
    else
        hr = atlhr + hr;
    end
    ok = true;
    while ok
        if hr > hrmark(1)
            hr = hr - 12;
        elseif hr <= 0
            hr = hr + 12;
        else
            ok = false;
        end
    end
    plot([0, (0.6*cos(hrmark(hr)))], ...
         [0, (0.6*sin(hrmark(hr)))], 'b');
    minmark = linspace(0, 2*pi, 61);
    minutes = str2num(minutes(2:end))+30;
    plot([0, 0.9*cos(minmark(minutes))], ...
         [0, 0.9*sin(minmark(minutes))], 'r');
    title(shift{ndx}{1});
    axis square
    axis off
end

end