在數據框中用一個參數計算一個新行

Question

我想在現有數據框中用一個參數（worker_id）計算一個新的行（difference_mean_by_worker_id）和平均值（差異）。每一個worker_id的差異的平均值應該在新行中相同。 像這樣：

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謝謝，蒂姆

Answer 1

這裏是一個data.table解決方案：

library(data.table); 

# make the data 
df = data.table(
    worker_id = c(111, 111, 222, 222), 
    difference = c(5, 3, 5, 2) 
); 

# calculate mean difference 
df_new = df[ 
    , 
    # make a new column called "difference_mean_by_worker_id" to be the mean of 
    # "difference" 
    "difference_mean_by_worked_id" := mean(x = difference), 
    # grouped by worker_id 
    by = "worker_id" 
]; 

df_new; 

     worker_id difference difference_mean_by_worked_id 
1:  111   5       4.0 
2:  111   3       4.0 
3:  222   5       3.5 
4:  222   2       3.5 

這個腳本計算平均值由worker_id分區組中的距離。希望這可以幫助！