1. Introduction To Matlab Class 7
Instructors: Hristiyan (Chris) Kourtev
and Xiaotao Su, PhD

2. cell arrays ‘cat’ 3 ‘zebra’ ‘dog’ 5 9 10 3 9 5
cell arrays are a different data type
they are like a matrix where each element is any other data type
example_cell_array = {‘cat’, 3, [5, 9];
‘zebra’, [10, 3; 9, 5], ‘dog’};
‘cat’ 3
‘zebra’
‘dog’ 5 9 10 3 9 5

3. ‘cat’ 3 ‘zebra’ ‘dog’ 5 9 10 3 9 5 a = example_cell_array{2, 3}
example_cell_array{2, 1} = a
example_cell_array{2, 2}(2, 1)

4. cell2csv Works just like csvwrite
Will only work with “simple” cell arrays
no numeric vectors or matrices
data = {‘trial number’, ‘time’, ‘color’, ‘response’; , 5.99, ‘blue’, 3; , 4, ‘green’, 2;
3, 55, ‘yellow’, 2}
cell2csv(‘somefile.csv’, data);
!Note: cell2csv is not a built in Matlab function. Download it here:

5. important note to add one data element to a cell array
data{5, 3} = 'yellow’
curly braces
To add one row of data
data(5, :) = {4, 2.93, ‘yellow’, 4}
parenthesis
data(trial+1, :) = {trial, time, color, response}

6. response = input('What is it?');
stop_time = GetSecs;
response_time = stop_time - start_time;
is_correct = (response==random_num);
if(is_correct)
disp('Right!');
else
disp(['Wrong! The correct answer was ', ...
num2str(random_num)]);
end
disp('Press any key to continue');
pause
disp(' ');
%record data
guessing_game_data(t, :) =...
[t, response_time, response, ...
random_num, is_correct ];
%guessing_game.m %test to see if subject is psychic clear all; %settings num_trials = 5; highest_number = 3; %get info subject_name = input('What is your name?', 's'); for t = 1:num_trials %trial set up random_num = ceil(rand*highest_number); %perform experiment start_time = GetSecs; disp('I am thinking of a number between'); disp([' 1 and ', num2str(highest_number)]);
%data_storage
csvwrite([subject_name, '.csv'], …
guessing_game_data);

7. response = input('What is it?');
stop_time = GetSecs;
response_time = stop_time - start_time;
is_correct = (response==random_num);
if(is_correct)
disp('Right!');
else
disp(['Wrong! The correct answer was ', ...
num2str(random_num)]);
end
disp('Press any key to continue');
pause
disp(' ');
%record data
guessing_game_data(t, :) =...
[t, response_time, response, ...
random_num, is_correct ];
%guessing_game.m %test to see if subject is psychic clear all; %settings num_trials = 5; highest_number = 3; %get info subject_name = input('What is your name?', 's'); for t = 1:num_trials %trial set up random_num = ceil(rand*highest_number); %perform experiment start_time = GetSecs; disp('I am thinking of a number between'); disp([' 1 and ', num2str(highest_number)]);
%set up labels
guessing_game_data = {‘trial’, ‘response time’, … ‘response’, ‘random_num’, ‘is_correct?’}
%record data
guessing_game_data(t+1, :) = …
{t, response_time, response, random_num, is_correct}
%data_storage
csvwrite([subject_name, '.csv'], …
guessing_game_data);
cell2csv

8. Task - color differentiation (part 1)
Take subject name
screen_setup
trial loop (start with 5) color = [rand*255, rand*255, rand*255]
put circles 1-4 on the screen
one of the four circles will be slightly off (start with +/-50), color from the others on one of the three color dimensions (randomly chose dimension); careful that your deviation doesn’t go >255 or <0
The subject will click on the circle they feel is different
record data (whatever would be useful)
if the subject was right in the last loop, the amount the color is off is cut in half, otherwise, increase by half
save trial data to csv
tip: make a function to determine if the cursor is in a shape
function is_in = in_shape(vect, mouse_x, mouse_y)

9. Task - color differentiation (part 2)
Further additions:
allow the subject to press to select a circle (using KbCheck)
put numbers in the circles
Hint: You need to use the following commands:
Screen('TextFont', window, fontName*); Screen('TextSize', window, fontSize**);
Screen('DrawText', window, textString, x, y, textColor); *fontName can be “Arial”, “Verdana” or other
*fontSize can be any number. Start with around 20 and adjust as needed