{"id":3200,"date":"2023-07-18T17:44:30","date_gmt":"2023-07-18T17:44:30","guid":{"rendered":"https:\/\/statorials.org\/cn\/pandas-groupby-%e5%8f%98%e6%8d%a2\/"},"modified":"2023-07-18T17:44:30","modified_gmt":"2023-07-18T17:44:30","slug":"pandas-groupby-%e5%8f%98%e6%8d%a2","status":"publish","type":"post","link":"https:\/\/statorials.org\/cn\/pandas-groupby-%e5%8f%98%e6%8d%a2\/","title":{"rendered":"\u5982\u4f55\u5728 pandas \u4e2d\u4f7f\u7528 groupby() \u548c transform() \u51fd\u6570"},"content":{"rendered":"

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\u60a8\u53ef\u4ee5\u4f7f\u7528\u4ee5\u4e0b\u65b9\u6cd5\u5728pandas DataFrame\u4e2d\u4e00\u8d77\u4f7f\u7528groupby()<\/strong>\u548ctransform()<\/strong>\u51fd\u6570\uff1a<\/span><\/p>\n

\u65b9\u6cd51\uff1a\u4f7f\u7528\u5185\u7f6e\u51fd\u6570\u7684groupby()\u548ctransform()<\/strong><\/span><\/p>\n

 df[' new<\/span> '] = df. groupby<\/span> (' group_var<\/span> ')[' value_var<\/span> ']. transform<\/span> (' mean<\/span> ')\n<\/strong><\/pre>\n
\u65b9\u6cd52\uff1a\u5c06groupby()\u548ctransform()\u4e0e\u81ea\u5b9a\u4e49\u51fd\u6570\u7ed3\u5408\u4f7f\u7528<\/strong><\/span><\/p>\n
 df[' new<\/span> '] = df. groupby<\/span> (' group_var<\/span> ')[' value_var<\/span> ']. transform<\/span> ( lambda<\/span> x: some function)<\/strong><\/pre>\n
\u4ee5\u4e0b\u793a\u4f8b\u5c55\u793a\u4e86\u5982\u4f55\u5728\u5b9e\u8df5\u4e2d\u4f7f\u7528\u4ee5\u4e0b pandas DataFrame \u7684\u6bcf\u79cd\u65b9\u6cd5\uff1a<\/span><\/p>\n
 import<\/span> pandas as<\/span> pd\n\n#createDataFrame<\/span>\ndf = pd. DataFrame<\/span> ({' team<\/span> ': ['A', 'A', 'A', 'A', 'B', 'B', 'B', 'B'],\n                   ' points<\/span> ': [30, 22, 19, 14, 14, 11, 20, 28]})\n\n#view DataFrame\nprint<\/span><\/span> (df)\n\n  team points\n0 to 30\n1 to 22\n2 to 19\n3 to 14\n4 B 14\n5 B 11\n6 B 20\n7 B 28\n<\/b><\/pre>\n
\u793a\u4f8b 1\uff1a\u5c06 groupby() \u548c transform() \u4e0e\u5185\u7f6e\u51fd\u6570\u7ed3\u5408\u4f7f\u7528<\/strong><\/span><\/h3>\n
\u4ee5\u4e0b\u4ee3\u7801\u6f14\u793a\u4e86\u5982\u4f55\u4f7f\u7528groupby(<\/strong> ) \u548ctransform()<\/strong>\u51fd\u6570\u5411 DataFrame \u6dfb\u52a0\u4e00\u4e2a\u540d\u4e3amean_points \u7684\u65b0\u5217\uff1a<\/span><\/p>\n
 #create new column called mean_points\ndf[' mean_points<\/span> '] = df. groupby<\/span> (' team<\/span> ')[' points<\/span> ']. transform<\/span> (' mean<\/span> ')\n<\/span>\n#view updated DataFrame\nprint<\/span> (df)\n\n  team points mean_points\n0 to 30 21.25\n1 to 22 21.25\n2 A 19 21.25\n3 to 14 21.25\n4 B 14 18.25\n5 B 11 18.25\n6 B 20 18.25\n7 B 28 18.25<\/span><\/span><\/strong><\/pre>\n
 A \u961f\u7403\u5458\u7684\u5e73\u5747\u5f97\u5206\u4e3a21.25<\/strong> \uff0cB \u961f\u7403\u5458\u7684\u5e73\u5747\u5f97\u5206\u4e3a18.25<\/strong> \uff0c\u56e0\u6b64\u8fd9\u4e9b\u503c\u88ab\u76f8\u5e94\u5730\u5206\u914d\u7ed9\u65b0\u5217\u4e2d\u7684\u6bcf\u4e2a\u7403\u5458\u3002<\/span><\/p>\n
\u8bf7\u6ce8\u610f\uff0c\u6211\u4eec\u8fd8\u53ef\u4ee5\u4f7f\u7528\u53e6\u4e00\u4e2a\u5185\u7f6e\u51fd\u6570\uff08\u4f8b\u5982sum()\uff09<\/strong>\u6765\u521b\u5efa\u4e00\u4e2a\u65b0\u5217\uff0c\u663e\u793a\u6bcf\u4e2a\u56e2\u961f\u7684\u5f97\u5206\u603b\u548c\uff1a<\/span><\/p>\n
 #create new column called sum_points\ndf[' sum_points<\/span> '] = df. groupby<\/span> (' team<\/span> ')[' points<\/span> ']. transform<\/span> (' sum<\/span> ')\n<\/span>\n#view updated DataFrame\nprint<\/span> (df)\n\n  team points sum_points\n0 to 30 85\n1 to 22 85\n2 A 19 85\n3 to 14 85\n4 B 14 73\n5 B 11 73\n6 B 20 73\n7 B 28 73<\/span><\/span><\/strong><\/pre>\n
 A\u961f\u7403\u5458\u7684\u5f97\u5206\u603b\u548c\u4e3a85<\/b> \uff0cB\u961f\u7403\u5458\u7684\u5f97\u5206\u603b\u548c\u4e3a73<\/strong> \uff0c\u56e0\u6b64\u8fd9\u4e9b\u503c\u88ab\u76f8\u5e94\u5730\u5206\u914d\u7ed9\u65b0\u5217\u4e2d\u7684\u6bcf\u4e2a\u7403\u5458\u3002<\/span><\/p>\n
\u793a\u4f8b 2\uff1a\u5c06 groupby() \u548c transform() \u4e0e\u81ea\u5b9a\u4e49\u51fd\u6570\u7ed3\u5408\u4f7f\u7528<\/strong><\/span><\/h3>\n
\u4ee5\u4e0b\u4ee3\u7801\u6f14\u793a\u5982\u4f55\u4f7f\u7528groupby(<\/strong> ) \u548ctransform()<\/strong>\u51fd\u6570\u521b\u5efa\u4e00\u4e2a\u81ea\u5b9a\u4e49\u51fd\u6570\uff0c\u7528\u4e8e\u8ba1\u7b97\u5404\u81ea\u7403\u961f\u4e2d\u6bcf\u4e2a\u7403\u5458\u7684\u603b\u5f97\u5206\u767e\u5206\u6bd4\uff1a<\/span><\/p>\n
 #create new column called percent_of_points\ndf[' percent_of_points<\/span> '] = df. groupby<\/span> (' team<\/span> ')[' points<\/span> ']. transform<\/span> ( lambda<\/span> x:x\/ x.sum<\/span> ())\n<\/span>\n#view updated DataFrame\nprint<\/span> (df)\n\n  team points percent_of_points\n0 A 30 0.352941\n1 A 22 0.258824\n2 A 19 0.223529\n3 A 14 0.164706\n4 B 14 0.191781\n5 B 11 0.150685\n6 B 20 0.273973\n7 B 28 0.383562\n<\/span><\/span><\/strong><\/pre>\n
\u4ee5\u4e0b\u662f\u5982\u4f55\u89e3\u91ca\u7ed3\u679c\uff1a<\/span><\/span><\/p>\n