MATLAB exercise solutions (Century College, CSCI 1081, Fall 2024)

a = [1 2 3 4 5 6];
%a = [1:6]; % also works
 
disp(a * 7);

% not provided.

a = [2 3 1 5; 1 0 3 1; 0 2 -3 2; 0 2 3 1];
% either works for multiplying a matrix with a scalar:
disp(a * 7);
disp(a .* 7);

a = [2 3 1 5; 1 0 3 1; 0 2 -3 2; 0 2 3 1];
b = inv(a);
disp(a * b); % result is (approx.) identity matrix

a = [2 3 1 5; 1 0 3 1; 0 2 -3 2; 0 2 3 1];
b = [1 2 3; 10 20 30; 0.1 0.2 0.3];
matrixinfo(a);
matrixinfo(b); % square matrix of Inf values

function matrixinfo(m)
% matrix_info(m)
% Tell the user whether mtx is a square matrix. If it is a square matrix, 
% display the matrix's transpose and inverse.
 
msize = size(m);
if ndims(m) == 2 && msize(1) == msize(2),
    disp('It''s a square matrix.');
    disp('The transpose is:');
    disp(m');
    disp('The inverse is:');
    disp(inv(m));
else
    disp('The matrix isn''t square.');
end % if
end % function

% Input data for three monkeys
NUM_MONKEYS = 3;
NUM_DAYS = 5;
 
% initialize data to -1)
data = ones(NUM_MONKEYS, NUM_MONKEYS) * -1;
 
% Get monkey data
for monkey = 1:NUM_MONKEYS,
    disp('----------');
    % enter row data as days of week
    for day = 1:NUM_DAYS,
        is_valid = false;
        while ~is_valid,
            prompt = ['Monkey ' num2str(monkey) ', day ' num2str(day) ': '];
            data(monkey, day) = input(prompt);
            is_valid = data(monkey, day) >= 0;
            if ~is_valid,
                disp('Try again.');
            end; % if
        end % while
    end % inner for
end % outer for
 
% for each column, compute the average:
avgeaten = zeros(1, NUM_DAYS);
for day = 1:NUM_DAYS,
    avgeaten(day) = mean(data(:, day));
end % for
 
% Display report
disp('=====================================');
disp('The average amount eaten on each day:');
disp(avgeaten);
 
disp(['The least amount eaten this week: ' num2str(min(min(data))) ]);
disp(['The greatest amount eaten this week: ' num2str(max(max(data))) ]);
disp('=====================================');