get_transition_matched_sequence

random_matched_transitions.py

"""written by O. Lindemann"""

import numpy as np

np.random.seed()

def get_transition_matched_sequence(conditions, n_transition_repetitions):
    """ returns of sequences of conditions, were each transistion is balanced
    """

    # makes a n-n matix (n = number of conditions) that codes the transitions.
    #    row = previous condition
    #    column = current condition
    #
    # Draws a new condition and keeps track of transtions using the
    # transistion matrix. If transition occured too often, it draws a new
    # condition. If no solution is found it redraws.

    n_conditions = len(conditions)
    required_sequence_length = n_conditions**2 * n_transition_repetitions
    cnt_mtx =  np.zeros([n_conditions, n_conditions])
    seq = []
    current = np.random.randint(n_conditions)
    while len(seq) < required_sequence_length:
        previous = current
        cnt = 0
        while True:
            current = np.random.randint(n_conditions)
            if cnt_mtx[previous, current] < n_transition_repetitions:
                cnt_mtx[previous, current] += 1
                seq.append(current)
                break
            else:
                # transistions too often, try again
                cnt += 1
                if cnt >  n_conditions * 50:
                    # no solution, redraw
                    return get_transition_matched_sequence(conditions,
                         n_transition_repetitions)
    return np.array(conditions)[seq]

def get_transition_dict(sequence):
    """returns a dict with the transitions

    mainly used for testing transistions of sequences
    """

    prev = None
    transition_dict =  {}
    for cur in sequence:
        if prev is not None:
            s = "{0}-{1}".format(prev, cur)
            if transition_dict.has_key(s):
                transition_dict[s] += 1
            else:
                transition_dict[s] = 1
        prev = cur
    return transition_dict


if __name__ == "__main__":

    seq = get_transition_matched_sequence(conditions = ["A", "B", "C", "D"],
                        n_transition_repetitions = 10)
    print seq

    print "testing transitions"
    print get_transition_dict(seq)