>Psychtoolbox>PsychProbability

BalanceTrials balances a set of factors given the factor levels. It is
identical to BalanceFactors except that the first argument is the number
of trials desired. It outputs one or more vectors containing factor
values for each trial, balanced and, optionally, randomized.

[F1, F2, …] = BalanceTrials(NTRIALS, RND, LVL1, LVL2, …)

BalanceTrials must be called with three or more input arguments. The
first argument, NTRIALS, specifies the number of trials desired. The
second argument, RAND, determines whether or not the returned factors
should be shuffled (non-zero values lead to shuffling).

The remaining input arguments specify the levels for each of a set of
factors. Factor levels can be specified as numeric vectors or cell
arrays (e.g., for category names). The returned factor lists will be the
same class as the corresponding levels.

WARNING: If NTRIALS is not a multiple of the product of the number of
levels, then the actual number of trials generated will be more than
NTRIALS. To detect this situation, test whether numel(F1) == NTRIALS.

EXAMPLES:

[targetPresent, setSize] = BalanceTrials(80, 0, 0:1, [3 6 9 12]);

[target, setSize, dur] = …
BalanceTrials(72, 1, [0 1], [4 8 12], [0 100 200]);

[samediff, mask] = …
BalanceTrials(20, 1, {‘same’, ‘diff’}, {‘pattern’, ‘meta’});

See also: BalanceFactors