Unnamed: 0 country hemisphere zone ID_month month crop variable diag non-diag stability_factor v1_stability_factor v2_stability_factor v3_stability_factor
0 0 Mexico Southern tropical 1 Jan Maize DV 75 325 0.230769231 0 50 25
67 0 Canada Northern temperate 1 Jan Winter Wheat DV 81.24552083 318.7544792 0.254884327 24.55528427 24.07126611 24.31327519
85 0 Ukraine Northern temperate 1 Jan Winter Wheat DV 133.0328009 266.9671991 0.498311408 33.77390206 32.04552044 32.90971125
93 0 India Northern temperate 1 Jan Soybean DV 163.9592092 236.0407908 0.694622352 40.33741643 51.85145586 46.09443615
98 0 United States Of America Northern temperate 1 Jan Winter Wheat DV 126.1548643 273.8451357 0.460679588 28.50863898 37.64939577 33.07901737
106 0 China Northern temperate 1 Jan Maize DV 118.6847373 281.3152627 0.421892279 34.69179042 43.85685473 39.27432258
23 0 South Africa Northern temperate 1 Jan Maize DV 139.5177365 260.4822635 0.535613192 54.10327834 43.14757235 48.62542534
在上面的数据框中，我想通过分别对北半球和南半球国家进行平均来添加平均列diag non-diag stability_factor v1_stability_factor v2_stability_factor v3_stability_factor的2行。