计算点互信息矩阵PPMI代码

以下是计算点互信息矩阵PPMI的Python代码：

import numpy as np

def compute_PPMI_matrix(co_matrix):
    # Compute the sum of all elements in the co-occurrence matrix
    N = np.sum(co_matrix)
    # Compute the sum of each row and column in the co-occurrence matrix
    row_sum = np.sum(co_matrix, axis=1)
    col_sum = np.sum(co_matrix, axis=0)
    # Compute the total number of rows and columns in the co-occurrence matrix
    num_rows, num_cols = co_matrix.shape
    # Initialize the PPMI matrix
    PPMI_matrix = np.zeros((num_rows, num_cols))
    # Compute the PPMI matrix
    for i in range(num_rows):
        for j in range(num_cols):
            pmi = np.log2((co_matrix[i,j]*N)/(row_sum[i]*col_sum[j]))
            PPMI_matrix[i,j] = max(pmi, 0)
    return PPMI_matrix

其中，输入参数`co_matrix`为共现矩阵，输出为PPMI矩阵。注意，由于PPMI矩阵的值可能小于0，因此在计算PPMI值时需要取max(pmi, 0)。