Function _expected

pattern/metrics.py:732–745

Returns the table of (absolute) expected frequencies from the given table of observed frequencies.

(observed)

UPPER = "upper" 

def _expected(observed):
    """ Returns the table of (absolute) expected frequencies
        from the given table of observed frequencies.
    """
    O = observed
    if len(O) == 0:
        return []
    if len(O) == 1:
        return [[sum(O[0]) / float(len(O[0]))] * len(O[0])]
    n = [sum(O[i]) for i in range(len(O))]
    m = [sum(O[i][j] for i in range(len(O))) for j in range(len(O[0]))]
    s = float(sum(n))
    # Each cell = row sum * column sum / total.
    return [[n[i] * m[j] / s for j in range(len(O[i]))] for i in range(len(O))]

def pearson_chi_squared_test(observed=[], expected=[], df=None, tail=UPPER):
    """ Returns (X2, P) for the n x m observed and expected data (containing absolute frequencies).