Numerical Data Structures

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cell

vector = row/column

matrix = group of vectors

• is a rectangle

array = 3d matrix

Initialize matrix matrix = [1 1;2 2]

• ; = new row
• <space> = next column

Specify # of cells

• matrix = zeros(numRows, numColumns)
• matrix = ones(numRows, numColumns)
  • or ones([numRows numColumns])

Call data from all numRows rows or numColumns columns

• replace with :
• ex: matrix(:,4)

vector = [1:100]

• fills vector with numbers 1 to 100

vector(row, col) = 10

• change cell value

vector(row, col)

• get number and print it out

sum(vector)

• sums all numbers in vector

prod(vector)

• multiply everything in vector

Math between two vectors/matrices

• use +, -, *, /

Math between correlating cells in vectors/matrices

• use +, -, .*, ./

vector = vector';

• make the row vector into a column vector

matrix(:)

• take all cells in the matrix

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Other Data Structures

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Strings are in single quotes ‘’

num2string(var);

• change data type

string2num(var);

• change data type

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Miscellaneous Syntax

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NaN = null

% = comment

... at the end of the line when you want to press enter

• ex:

    var1 *...
    var2
  

• put semicolons in scripts
  • won’t print onto command window

lowerLimit:upperLimit

• vector with all numbers from lowerLimit to upperLimit

~ = not

|| = or

&& = and

for loops for i = start:end %do something end

if statemtents if %condition %action else %action end

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Random Functions

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vector = xlsread('fileName.extension')

• Read Exel file

image = imread('imagename');

• read image

linspace(start, end, n_points);

• returns equally spaced points
• includes starting and end points

[x,y] = meshgrid(xVector, yVector)

• returns all possible coordinates of pts
• use with linspace

size(vector, <row or column as in 1 or 2>)

• returns numRows, numColumns
• don’t specify row or column if want both

imageB = imresize(imageA, scale);

imageB = imresize(imageA, [numRows, numCols]);

• imageB has numRows rows and numCols cols
• or put NaN as one of them to preserve aspect ratio

imshow(image);

• make a window with the image on it

sind(theta)

• sin

cosd(theta)

• cos

repmat(vector, numTimes)

• repeat the vector numTimes horizontally and vertically

repmat(vector, numRows, numColumns)

• have that many total rows/cols

shuffle(vector)

• change up the order of all cells, use with repmat

shuffle(vector, dimension)

• dimension: 1 = Rows change, 2 = Columns change, 3 = next dimension changes, etc

vertcat(vector, vector2, vector3, ...)

• stacks vectors ontop of each other

horzcat(vector, vector2, vector3, ...)

• stacks vectors side to side

RandStream.setGlobalStream(RandStream('mt19937ar', 'seed', sum(100*clock)));

• put it everywhere just in case you want a random number (for real randomness)

randperm(upperLimit, numCells);

• can’t get the same number twice

randperm(upperLimit)

• numbers 1~upperLimit are reordered

randi(upperLimit);

• get one random number

randi(upperLimit, numRows, numCols);

• random numbers in matrix numRows x numCols

randi([lowerLimit, upperLimit]);

• number from lowerLimit to upperLimit

randsample(upperLimit, numCells);

• numCells number of random numbers

randsample([1 2 3], 2)

• numCells number of rand numbers from the vector

any(vector)

• returns true if any of cells is nonzero

floor(num)

• returns num rounded down to whole number

ismember(element, vector)

• returns true if element is found inside the vector

WaitSecs(seconds);

• how long to wait

GetSecs()

• get seconds from start of program
• use to make sure the time intervals are right

[keyIsDown, secs, keyCode] = KbCheck()

• if have different keyboards, put 1/2/3/4/5 in parenthesis for specific keyboard
• keyIsDown = any button down (1 or 0 => true or false)
• secs = time from GetSecs()
• keyCode = key that is down
  • ex: strcmp(‘s’, KeyName(keyCode)), see if it is ‘s’

[x,y,clicks] = GetMouse()

• x, y = mouse position coordinates
• if clicks = [0,0,0] => no click, [1, 0, 0] = left click
• test with any(clicks)

GetClicks()

• get number of mouse clicks

strcmp(string1, string2)

• returns true if identical, false if not

string = strcat(string1, string2)

• combine string1 and string2

KeyName('UnifyKeyNames')

• make codes from key presses the same from macs/windows/etc

save(fileName, 'variable')

• ex: save('result', 'p', 'q');
• save some variables in a file (.mat)

string = upper(string)

• all letters uppercase

isdir(directoryString)

• true if there already is a directory with that name, false if no
• example of directoryString is from pwd()

mkdir(directoryString)

• create a folder with directory directoryString

sortrows(matrix, colNum)

• make numbers in the colNum-th column be in ascending order

resizem(input, scale)

resizem(input, [numRows, numCols])

• expand and contract matrix

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Command Line Commands

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COMMANDS CAN BE PUT INTO SCRIPTS

pwd

• print your directory
• usage examples:

    rootDir = pwd();
    resultsDir = [rootDir '/results/']
    if ~isdir(resultsDir) %if don't have this directory already
        mkdir(resultsDir) %make the directory/folder
    end
  

cd(folderName)

• change directory
• go one level up => cd ..

ls

• list of files in the folder

clear all

• clears variables from other experiments

clc

• clear command window

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Keyboard Shortcuts

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ctrl+c then s then c then a then enter

• bring back window (if it crashes)
• might need to alt+tab (switch windows) before doing above

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Psychtoolbox

===============

A library for psychology experiments

Screen has many settings

• access w/ Screen('something', <specific>, <more specific>, <etc>);
• Screen('CloseAll');
  • closes all screens
• Screen('Preference', 'SkipSyncTests', 1);
  • yes to skipping sync tests

[window, rect] = Screen('OpenWindow', 0, [], [500 500 700 700]);

• open the window
  • 0 = open on this monitor
  • 1 = open on other monitor
• 2nd matrix = where the screen will be
• window = pointer
• rect = (startX, startY, endX, endY)
  • corner coordinates;
• Screen puts data into window/rect

x = Screen('MakeTexture', window, uint8(image));

• uint8 because colors in image can’t be > 255

Screen('DrawTextures', window, x);

• draw the texture. x is from function above

Screen('DrawTextures', window, tid(rand_oranges(i,:)), [], xy_rect, orientation);

• xy_rect = corners of each picture
• orientation = degrees of rotation=========================================================================

A = Screen('Flip', window);

• display onto monitor
• usually don’t need A

Screen('Flip', window, A + seconds);

• show a blank screen (if nothing is made with window) second seconds later
• more accurate than WaitSecs()

KbWait();

• wait for keyboard input before going on

• how to get rid of background of image

  • add transparent mask ontop
  • mask must be same size as image