位數由組中data.table

Question

切我想這樣做位數切口（切成具有相等數量的點的n個二進制位）爲每個組

qcut = function(x, n) { 
    quantiles = seq(0, 1, length.out = n+1) 
    cutpoints = unname(quantile(x, quantiles, na.rm = TRUE)) 
    cut(x, cutpoints, include.lowest = TRUE) 
} 

library(data.table) 
dt = data.table(A = 1:10, B = c(1,1,1,1,1,2,2,2,2,2)) 
dt[, bin := qcut(A, 3)] 
dt[, bin2 := qcut(A, 3), by = B] 

dt 
A  B bin  bin2 
1: 1 1 [1,4] [6,7.33] 
2: 2 1 [1,4] [6,7.33] 
3: 3 1 [1,4] (7.33,8.67] 
4: 4 1 [1,4] (8.67,10] 
5: 5 1 (4,7] (8.67,10] 
6: 6 2 (4,7] [6,7.33] 
7: 7 2 (4,7] [6,7.33] 
8: 8 2 (7,10] (7.33,8.67] 
9: 9 2 (7,10] (8.67,10] 
10: 10 2 (7,10] (8.67,10] 

這裏不進行分組的切口是正確的 - 數據位於在垃圾桶裏。但是小組的結果是錯誤的。

我該如何解決這個問題？

Answer 1

這是一個處理因素的錯誤。請檢查它是否已知（或在開發版本中修復），否則將其報告給data.table錯誤跟蹤器。

qcut = function(x, n) { 
    quantiles = seq(0, 1, length.out = n+1) 
    cutpoints = unname(quantile(x, quantiles, na.rm = TRUE)) 
    as.character(cut(x, cutpoints, include.lowest = TRUE)) 
} 

dt[, bin2 := qcut(A, 3), by = B] 
#  A B bin  bin2 
# 1: 1 1 [1,4] [1,2.33] 
# 2: 2 1 [1,4] [1,2.33] 
# 3: 3 1 [1,4] (2.33,3.67] 
# 4: 4 1 [1,4] (3.67,5] 
# 5: 5 1 (4,7] (3.67,5] 
# 6: 6 2 (4,7] [6,7.33] 
# 7: 7 2 (4,7] [6,7.33] 
# 8: 8 2 (7,10] (7.33,8.67] 
# 9: 9 2 (7,10] (8.67,10] 
#10: 10 2 (7,10] (8.67,10]