Exercises

Please complete each exercise or answer the question before reviewing the posted solution comments.

Use the clear command before starting your work on a new problem to ensure that any existing variable name assignments don't interfere with your work on the new problem.

1. Write a code fragment that uses an if statement nested inside a while loop to search a data vector for a target value and then displays the index of the target if it is found.

   If the target value is not found, it displays the message "target value not found".

   clear;
   data_vector = [ 0 10 9 34 57 8 32 7 8];  % the vector to search
   target = 8;                              % the target value
   
   index = 1; % index into data_vector, start at the beginning
   while index <= length(data_vector)   % while we haven't reached end of vector
       if data_vector(index) == target  % if we find the target value
           break                        % stop looking
       end
       index = index + 1;               % otherwise, update index and keep looking
   end
   
   % at this point, one of two things has happened:
   % 1) the target value was found and we broke out of the loop with the correct index
   % 2) the target value was not found and we stopped looping when index = length(data_vector) + 1
   
   if index <= length(data_vector)
       disp(['target value ', num2str(target), ' found at index ', num2str(index)])
   else
       disp(['target value ', num2str(target), ' not found'])
   end
   

2. Suppose Chris' hours for the week are stored in a data file named hours.m. For example, hours.m could contain the values:

   7.25
   9.5
   12.75
   6.5
   8.25

   Write a script that loads the hours and computes Chris' gross pay for the week (using the hours matrix). Chris gets overtime for any time that exceeds 8 hours in one day's shift. Use $7.53 as the hourly pay rate and 1.5 times that for the overtime pay rate.

   clear;
   load hours.m;   % loads hours for the week into the hours variable
   hourly = 7.53;
   overtime = hourly * 1.5;
   gross_pay = 0;
   for i = 1 : length(hours)  % for each day
       
       % if hours worked is 8 or fewer, then use hourly pay rate
       if hours(i) <= 8
           gross_pay = gross_pay + hours(i) * hourly;
       
       % otherwise, the hours worked is more than 8, 
       % and must also compute overtime pay
       else
           gross_pay = gross_pay + 8*hourly + (hours(i) - 8)*overtime;
       end
   end
   disp(['Weekly gross pay is $', num2str(gross_pay)])
   

3. Write a script that prints an L by H rectangle of asterisks, where L is the length and H is the height and these numbers are defined at the beginning of your script. For example if L is 7 and H is 4, your script should print out:

       *******
       *******
       *******
       ******* 

   H = 4;
   L = 7;
   for r = 1 : H
       stars = [];
       for c = 1 : L
           stars = [stars  '*'];
       end
       disp(stars);
   end

4. Modify your script from exercise 3 so that it prints out an L by H box of asterisks. For example if L is 7 and H is 4, your script should print out:

   *******
   *     *
   *     *
   ******* 

   H = 4;
   L = 7;
   for r = 1 : H
       stars = [];
       for c = 1 : L
           if r==1 | r==H | c==1 | c==L
               stars = [stars  '*'];
           else
               stars = [stars  ' '];
           end
       end
       disp(stars);
   end

5. Write a script that prints a L by L right triangle of asterisks, where L is defined at the beginning of your script. For example, if L is 4, your script should print out:

   *
   **
   ***
   **** 

   clear;
   L = 7;  % the length (and height) of the triangle
   
   for r = 1 : L                   % for each row in the triangle
       
       stars = [];
   
       % the number of *'s to display is the same as the row index
       % i.e. row 1 has 1 *, row 2 has 2 *'s, etc.
       for n = 1 : r
           stars = [stars '*'];
       end
       disp(stars);
   end