CS205 Intro. Computational Programming and Visualization
Practice Questions for Final Exam

The Final Exam (May 15 4-6pm in BA 259) will focus on these questions,
as well as the questions from the first midterm

NOTE: I hope you have examined the solution for midterm one Midterm 1 Solutions

I plan to pose these questions in the same manner as our first midterm. So you will be asked to give the contents of the MATLAB Workspace and some of the problems, that are still evolving, will involve user-defined functions.

Loops and Control Statements

• Suppose we have a vector containing a group of distance values that represent the distance of a cable car from the nearest tower. We want to generate a coresponding vector containing velocityies. If the cable car is within 30 feet of the tower, we use the equation:
  velocity = 0.425 + 0.00175 * d^2
  If the cable cable is further than 30 feet from the tower, we use the follwing equation:
  velocity = .625 + 0.12 * d - 0.00025 * d^2
  Assume there are 25 elements in the given vector d, and write the appropriate MATLAB code to compute the corresponding velocities. (p. 102)

• Consider the following switch/case statement
  

  % assume the input value is in centimeters and this MATLAB code
  % converts to the units specified by the variable, units
  x = 2.7;
  units = 'm';
  disp([' for input ' num2str(x) ' in centimeters, this fragment converts to '])
  switch units % convert x to centimeters
  	case {'inch','in'}
  		y = x * 2.54 
  	case {'feet','ft'}
  		y = x * 2.54 * 12 
  	case {'meter','m'}
  		y = x/100 
  	case {'millimeter','mm'}
  		y = x*10 
  	case {'centimeter','cm'}
  		y = x 
  	otherwise
  		disp(['Unknown Units: ' units])
  		y = nan;
  end
  disp( units )
  

  Give the output:

  With the same source fragment above, what output will be computed for the case of

  x = 1025;
  units = 'ft';
  

Strings

• Give the output for the following MATLAB commands:
  • y = 45; s = num2str(y); title = [ ' Data for ' s ' cows in a pasture']
  • msg = 'You''re right!'
  • msg(1:3)
  • msg(8:12)

  • v = ['Character strings having more than'
         'one row must have the same number '
         'of columns just like arrays!      ']
    

  • lawyers = char('Cockran', 'Shapiro', 'Clark', 'Darden')
  • size(lawyers)

Timing

The routines tic, toc were introduced to allow the programmer to determine the amount of CPU needed to complete a sequence of commands.

• In the switch code fragment above, indicate below were you could insert calls for timing

  % assume the input value is in centimeters and this MATLAB code
  % converts to the units specified by the variable, units
  x = 2.7;
  units = 'm';
  disp([' for input ' num2str(x) ' in centimeters, this fragment converts to '])
  switch units % convert x to centimeters
  	case {'inch','in'}
  		y = x * 2.54 
  	case {'feet','ft'}
  		y = x * 2.54 * 12 
  	case {'meter','m'}
  		y = x/100 
  	case {'millimeter','mm'}
  		y = x*10 
  	case {'centimeter','cm'}
  		y = x 
  	otherwise
  		disp(['Unknown Units: ' units])
  		y = nan;
  end
  disp( units )
  

Graphics

Vector Operations

Draw a rough diagram of the expect MATLAB output for the following sequence of commands:

x = linspace(0,10,100); % create data
y = sin(x);
z = (y>=0) .* y; 
z = z + 0.5 * (y<0);
z = (x <=8) .* z;
plot(x,z),...
xlabel('x'),ylabel('z = f(x)'), title('A Discontinuous Signal')

File I/O

Draw a rough diagram of the expected MATLAB output for the following sequence of commands (this will involve a separate file):

• % set up data
  x = 0:10; y = [x; x.^2];
  fid = fopen('exp.txt','w') % open a file for writes
  fprintf(fid,' %g %g \n ',y)
  

• What are the contents of the file exp.txt?