1 / 21

Introduction To Matlab Class 3

Introduction To Matlab Class 3. Instructors: Hristiyan (Chris) Kourtev and Xiaotao Su, PhD. Variables. Integers m = 5; % = [5] Doubles (Floating pt) n = 7.382; Character strings c1 = ‘beep’ ; % = [‘b’, ‘e’, ‘e’, ‘p’] c2 = ‘4’;

franz
Download Presentation

Introduction To Matlab Class 3

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Introduction To MatlabClass 3 Instructors: Hristiyan (Chris) Kourtev and Xiaotao Su, PhD

  2. Variables • Integers m = 5; % = [5] • Doubles (Floating pt) n = 7.382; • Character strings c1 = ‘beep’ ; % = [‘b’, ‘e’, ‘e’, ‘p’] c2 = ‘4’; • Arrays of numbers arr1 = [4, 5, 8, m]; arr2 = [m, n, 5.6, 0]; • Arrays of strings str1 = [c1; ‘blob’]; % same dimen. • Concatenating arrays of numbers arr3 = [arr1, arr2]; • Concatenating strings str2 = [c1,c2]; • Matrices mat1 = [4, 5; 6, 7]; mat2 = [arr1; arr2]; % same dimen. • Cell Arrays (later on)

  3. Boolean Expressions • Boolean operands • Boolean expressions either return 1 for true e.g. 5 == 5 or 0 for false e.g. 5 > 9 • Put expressions in parentheses so they get evaluated firste.g. 0 || (4<5)

  4. Loops (for and while) • For loopfor index = from:to % do somethingend • While loopwhile(condition) % do something % change something that affects value of “condition”end

  5. Loops (for and while) -- examples max_loops = 5; for index = 1:max_loops disp(index); end counter = 1; while(counter < max_loops)disp(counter); counter = counter + 1; end %nested loop example for k = 1:max_loops disp(‘k1’); for m = 1:3 disp(‘m’); end disp(‘k2’); end % outputs: % k1 m mm k2 k1 m mm k2 k1 mmm k2 k1 m mm k2 k1 mmm k2

  6. Commonly used functions • rand - generates a random decimal number between 0 and 1e.g. 0.3456 or 0.9993 or 0.0013 etc • ceil(num) – returns the next integer bigger than the inpute.g. ceil(5.56) 6 or ceil(2.1)  3 or ceil(6)  6 • floor(num) – returns the next integer, smaller than the inpute.g. floor(0.9)  0 or floor(-0.1)  -1 • To generate a random number between 0 & 20: ceil(rand*20)

  7. Commonly used functions -- continued m = [1, 2, 3, 4]; n = [1, 2, 3, 4; 5, 6, 7, 8]; k = [9; 8; 0]; • length(mat) – returns the length of a vector or a matrixe.g. length(m)  4, length(n)  4, lenth(k)  3 • size(mat,dim) – returns all the dimensions of a matrix/vectore.g. size(m)  [1, 4], size(n)  [2, 4], size(k)  [3, 1], size (n, 2)  4

  8. Multiple Input/Output Functions • Functions can have more than one input and more than one outpute.g. s = size(mat, dim); • Storing returned values in 2 or more separate variablese.g. [x, y] = size(mat); • Storing returned values in a vector/cell arraye.g. vals = size(mat);

  9. Collecting User Input & Using it • Take input from keyboardnum1=input('what is the first number?'); • Validation checks: - isstr(var)- isnum(var) • Converting from strings to numbers and back- num2str(var)- str2num(var)

  10. Screen drawing and psychtoolbox Screen Geometry Origin Coordinates are measured in pixels. X ----------- Positive -> Y Positive Max X and Y

  11. Basic Display Loop in PsychToolbox (PTB) % Open Window % while some condition is true do the following % draw something % make some changes % repeat % Close screen

  12. Basic Display Loop in PTB (code) % draw_stuff.m % % Draws stuff on the screen clear all; try which_screen=0; bg_color = [0, 0, 0]; [window_ptr, screen_dimensions]= … Screen(which_screen, … 'OpenWindow',bg_color); shape_dimensions = … screen_dimensions/2; tic; while (toc < 5) % move shape shape_dimensions = … shape_dimensions + [0,5,0,5]; % draw shape Screen(window_ptr, 'FillRect', … [0,0,255], shape_dimensions); % flip buffer and repeat Screen(‘Flip’, window_ptr); end clear Screen; catch clear Screen; end

  13. Moving Shapes around the Screen • Shapes are defined by an array of numbers e.g. sh1 = [10, 15, 40, 45] ; % [x1, y1, x2, y2] • To move a shape in the x direction by 5 pixels we need to increment both x coordinates by 5e.g. sh1(1) = sh1(1) +5; sh1(3) = sh1(3) +5 or use another array: sh1 = sh1 + [5, 0, 5, 0]; • Same for moving in the y direction • Increment both if you want to move diagonally

  14. Task 1 – Mousing Around • Draw a green circle of radius 30 pixels, whose location on the screen is controlled by the mouse • Change the color of the circle to red when a button is clicked and back to green when released Hints: You will need to use the following functions • Get input from the mouse[mouse_x, mouse_y, buttons] = GetMouse(window_ptr); • Hide and show the windows cursor:HideCursor, ShowCursor • Draw a circle:Screen(window, 'FillOval', dot_color, cursor_dim); • If sum(buttons)>0, a button has been clicked

  15. while(toc<5) • [mouse_x, mouse_y, buttons] = GetMouse; • if(sum(buttons)>0) • dot_color = red; • else • dot_color = green; • end • cursor = [ mouse_x-dot_r, mouse_y-dot_r, ... • mouse_x+dot_r, mouse_y+dot_r]; • Screen(window_ptr, 'FillOval', dot_color, cursor); • Screen('Flip', window_ptr); • end • clear Screen; • ShowCursor; • catch • clear Screen; • ShowCursor; • end % mousingAround.m clear all; try which_screen=0; bg_color = [0, 0, 0]; [window_ptr, screen_dimensions]= … Screen(which_screen, … 'OpenWindow', bg_color); dot_r = 20; %radius of cursor HideCursor; green = [0, 255, 0]; red = [255,0, 0]; tic

  16. Skip Sync Tests • Add to your program before opening the new screenScreen('Preference','SkipSyncTests', 1);

  17. Direction/Velocity Vectors • A vector has both magnitude and direction • Direction = [x,y] • Magnitude = v = √(x2+y2) = sqrt(x^2 + y^2) % Pythagorean x v y x

  18. Detecting Collisions With Borders rect1 = [10, 10, 50, 50]; % [x1, y1, x2, y2] screen_dimensions = [0, 0, 1280, 1024]; • Collision w/ top border if: rect1(2) <= screen_dimensions(2) • Collision w/ left border if: rect1(1) <= screen_dimensions(1) • Collision w/ bottom border if: rect1(4) >= screen_dimensions(4) • Collision w/ right border if: rect1(3) >= screen_dimensions(2)

  19. Task 2 – Bouncing off the walls • Modify your existing program to add 2 blue squares that start off in a random direction at speed 5 and 7 pixels respectively and bounce off the walls Hints: • Will need to use direction vectors • Will need to use the Pythagorean theorem to calculate the direction vectors • If a square bumps into the left or right walls, invert (multiply by -1) the x component of its velocity vector • If a square bumps into the left or right walls, invert (multiply by -1) the y component of its velocity vector

  20. Task 3 – Click, Click Modify your program to: • Make the squares clickable. They should change color to purple when clicked. Hint: Purple = [255,0,255];

  21. if((mouse_x>shape1_rect(1))&... (mouse_x< shape1_rect(3))&... (mouse_y> shape1_rect(2))&... (mouse_y< shape1_rect(4))) shape1_color = purple; end if((mouse_x>shape2_rect(1))&... (mouse_x<shape2_rect(3))&... (mouse_y>shape2_rect(2))&... (mouse_y<shape2_rect(4))) shape2_color = purple; end

More Related