用python编写秩和比算法
时间: 2023-09-17 18:12:16 浏览: 78
以下是用Python编写的秩和比算法的示例代码:
```python
def ranksum_test(x, y):
"""
Conducts the rank sum test (Mann-Whitney U test) on two samples.
x: list or array of the first sample
y: list or array of the second sample
Returns the test statistic U and the p-value.
"""
from scipy.stats import rankdata
n1, n2 = len(x), len(y)
# Combine the samples and rank them
all_data = np.concatenate([x, y])
ranks = rankdata(all_data)
# Calculate the sum of the ranks for each sample
r1 = np.sum(ranks[:n1])
r2 = np.sum(ranks[n1:])
# Calculate U and adjust for ties
U = n1 * n2 + n1 * (n1 + 1) / 2 - r1
U_adj = min(U, n1 * n2 - U)
# Calculate the p-value using the normal approximation
z = (U_adj - n1 * n2 / 2) / np.sqrt(n1 * n2 * (n1 + n2 + 1) / 12)
p = 2 * (1 - norm.cdf(abs(z)))
return U, p
```
这个函数使用了Python的SciPy库来进行秩和比检验。该函数将两个样本组合在一起,并对它们进行排序,然后计算每个样本的秩之和。接下来,它使用秩和公式计算U统计量,并根据秩的大小调整U值,以便对于任何可能存在的平局进行了调整。最后,该函数使用正态近似计算p值,并返回U值和p值。
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