for i in range(len(clusters)):
            for j in clusters[i]:
                cov[i][0][0] = pow(stddev[i][0], 2)
                cov[i][1][1] = pow(stddev[i][1], 2)
                cov[i][0][1] += (j.x - mean[i][0]) * (j.y - mean[i][1])
                cov[i][1][0] = cov[i][0][1]
            cov[i][0][1] /= len(clusters)
            cov[i][1][0] = cov[i][0][1]