stats.py 文件源码

def awilcoxont(x,y):
    """
    Calculates the Wilcoxon T-test for related samples and returns the
    result.  A non-parametric T-test.

    Usage:   awilcoxont(x,y)     where x,y are equal-length arrays for 2 conditions
    Returns: t-statistic, two-tailed p-value
    """
    if len(x) <> len(y):
        raise ValueError, 'Unequal N in awilcoxont.  Aborting.'
    d = x-y
    d = N.compress(N.not_equal(d,0),d) # Keep all non-zero differences
    count = len(d)
    absd = abs(d)
    absranked = arankdata(absd)
    r_plus = 0.0
    r_minus = 0.0
    for i in range(len(absd)):
        if d[i] < 0:
            r_minus = r_minus + absranked[i]
        else:
            r_plus = r_plus + absranked[i]
    wt = min(r_plus, r_minus)
    mn = count * (count+1) * 0.25
    se =  math.sqrt(count*(count+1)*(2.0*count+1.0)/24.0)
    z = math.fabs(wt-mn) / se
    z = math.fabs(wt-mn) / se
    prob = 2*(1.0 -zprob(abs(z)))
    return wt, prob