## PsychProbability

##### >Psychtoolbox>PsychProbability

Psychtoolbox:PsychProbability.

Computation/Evaluation of probability distributions, basic sampling and

randomization.

BalanceFactors - Balance a set of factors given the factor levels.

BalanceTrials - Balance a set of factors given the factor levels. Takes alternative parameters wrt. BalanceFactors.

BuildMarkovK - Build covariance matrix for Markov process.

ChiSqrCumulative - Chi-squared distribution probability function.

ChiSquarePDF - Chi-squared distribution PDF.

ChooseKFromN - Randomly choose k distinct integers out of n.

ClockRandSeed - Seed rand() and randn() from clock.

CoinFlip - Bernoulli random variable.

CoinFlipPDF - Bernoulli distribution PDF.

ColMean - Take column means, works for one row matrices.

ColStd - Take column stds, works for one row matrices.

CombVec - Generate all possible combinations of input vectors.

CovToCorr - Compute matrix of correlations from covariance.

FindNeighborCorr - Find nearest neighbor correlations in data set.

MultiNormalDraw - Draw vectors from multivariate normal.

MultiNormalPDF - Compute multivariate normal PDF.

NormalCumulative - Univariate normal CDF

NormalDraw - Draw from univariate normal.

NormalPDF - Univariate normal PDF.

NormalProb - Compute probability of univariate normal in interval.

NRandPerm - Randomly select elements from a random permutation.

RandDim - Randomize matrix along any dimension.

Randi - Get random integer sample. Same as Ranint, but Denis prefers it.

RandLim - Generates a matrix of random numbers between a lower and upper limit.

RandSample - Get a random sample from a list.

RandSel - Randomly select elements from matrix, elements are replenished.

Ranint - Get random integer sample. Same as Randi, but David prefers it.

Sample - Get a random sample from a list.

Shuffle - Randomly reorder the entries of vector/matrix.

UniqueAndN - Returns unique elements of array and the number of times each element occurs in the array.

UniqueNoSorting - Returns elements of array in order of appearance or disappearance.

URandSel - Randomly select elements from matrix, elements are not replenished.

Combining CombVec and RandDim

Using CombVec and RandDim, it is very simple to generate all trials

in an experiment with a factorial design and then randomize these

trials:

cond_a = [1 2]; cond_b = [120 180]; ntrial = 2;

trial = CombVec(cond_a,cond_b);

trial =

1 2 1 2

120 120 180 180

trial = repmat(trial,1,ntrial); % each combination of conditions occurs ntrial times

trial(end+1,:) = [1:size(trial,2)]; % append trial number

trial = RandDim(trial,2); % shuffle trial order

trial =

2 1 1 2 1 1 2 2

120 180 180 180 120 120 120 180

6 3 7 8 5 1 2 4

BalanceFactors.m was contributed by David E. Fencsik (fencsik@gmail.com), thanks!

`Psychtoolbox/PsychProbability/Contents.m`