Matlab Class 7 Hristiyan Kourtev

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Matlab Class 7Hristiyan Kourtev Xiaotao Su,
Ph.D.Visual Psychophysicist IT Group
LeaderRutgers Center for Cognitive Science
(RuCCS)
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Accurate Timing

• GetSecs is a psychtoolbox function that provides
  highly accurate timing.
• It returns the number of seconds since the
  machine has started up
• To test precision on your machine,
  typeGetSecsTick

Command Window
a GetSecs GetSecs a GetSecs a GetSecs
a GetSecs a
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KbCheck

• KbCheck is used to check if a key is being
  pressed and to find out what key is being
  pressed.
• Returns three values
• key_press, secs, key_codeKbCheck

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KbCheck

• KbCheck is used to check if a key is being
  pressed and to find out what key is being
  pressed.
• Returns three values
• key_press, secs, key_codeKbCheck

Vector representing all of the input keys.
Elements in the vector are set to 1 if pressed or
0 if not
Time that this test took place (This is from
GetSecs function)
1 or 0 depending on if there was a key press
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Speed Test Game
disp('NOW!') timer GetSecs while
1 key_is_down, secs, key_code
KbCheck if(key_is_down)
break end end elapsed_time secs
- timer disp('Your time was ',
num2str(elapsed_time)) end

• speed_test.m
• tests your reaction time
• WaitSecs(1)
• disp('Ready?')
• num_sec_to_start rand51
• WaitSecs(num_sec_to_start)
• too_soon 0
• timer GetSecs
• while ((GetSecs-timer)ltnum_sec_to_start) ...
• (too_soon)
• too_soon, secs, keyCode KbCheck
• if(too_soon)
• break
• end
• end
• if(too_soon)
• disp('you pressed the key too early')
• else

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Task 1

• Make it so if someone presses a key too early,
  the program give a message and exits.

(Tipfirst remove WaitSecs

• key_press, secs, key_codeKbCheck

Vector representing all of the input keys.
Elements in the vector are set to 1 if pressed or
0 if not
Time that this test took place (This is from
GetSecs function)
1 or 0 depending on if there was a key press
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Speed Test Game
disp('NOW!') timer GetSecs while
1 key_is_down, secs, key_code
KbCheck if(key_is_down)
break end end elapsed_time secs
- timer disp('Your time was ',
num2str(elapsed_time)) end

• speed_test.m
• tests your reaction time
• WaitSecs(1)
• disp('Ready?')
• num_sec_to_start rand51
• WaitSecs(num_sec_to_start)
• too_soon 0
• timer GetSecs
• while ((GetSecs-timer)ltnum_sec_to_start) ...
• (too_soon)
• too_soon, secs, keyCode KbCheck
• if(too_soon)
• break
• end
• end
• if(too_soon)
• disp('you pressed the key too early')
• else

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What key was pressed?

• The third returned value is a vector representing
  all the keys with 1s for pressed keys and zeros
  for keys that arent pressed
• To find the value of the key, use
• key_name KbName(key_code)
• This will return a string corresponding to that
  key_code

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Simple program to find key mapping names

• get_key_name.m
• find out what the name of the key is
• WaitSecs(1)
• KbWait
• key_is_down, secs, key_code KbCheck
• name KbName(key_code)
• disp(name)

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KbName works the other way around as well

• As you have seen
• key_name KbName(key_code)
• You can also do the following
• return_key KbName(return)
• esc_key KbName(esc)
• up_key KbName(up)
• And this will get you the index of the element in
  the key_code vector that corresponds to that key

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key_code vector when esc is pressed
escs key code is 27
key_code vector
0 0 . 0 0 1 0 0 ..
(1) (2) . (25) (26) (27) (28) (29) .
Values
Indexes
So, key_code(27) is 1
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Exit on esc

• exit_on_esc.m
• esc_key KbName('esc')
• i 0
• while 1
• i i1
• key_is_down, secs, key_code KbCheck
• if(key_code(esc_key))
• break
• end
• end
• disp('Good Bye')

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Moving Dot
moving_dot.m clear all screen_setup up_key
KbName('up') down_key KbName('down') left_key
KbName('left') right_key KbName('right') esc
_key KbName('esc') shape 20, 20, 100,
100 color 255, 0, 255 tic
while toclt10 Screen(window, FillOval',
color, shape) flip key_is_down,
secs, key_code KbCheck
if(key_code(esc_key)) break
end end clear screen
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Task 2

• Draw a circle
• Make it so the arrow keys will move the circle
• Make sure the circle cannot go outside of the
  boundaries of the screen.

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Task 3 - color differentiation (part 1)

• Take subject name
• screen_setup
• trial loop (start with 5)color rand255,
  rand255, rand255
• 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 doesnt
  go gt255 or lt0
• 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)
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Task 3 - color differentiation (part 2)

• Further additions
• allow the subject to press 1 - 4 to select a
  circle (using KbCheck)
• put numbers in the circles
• Hint You need to use the following commands
• Screen('TextFont', window, fontName)Screen('Tex
  tSize', 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

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Deploying Matlab Programs on other machines

• The Matlab Builder/Deploytool deploytool
• The Matlab Component Runtime (MCR)
• Creating a standalone version of a Matlab program
  (Windows)
• Creating a standalone version of a Matlab program
  (OSX)
• The .NET Builder and deploying to the web