频率表包括未使用值的零，在数据表上 [英] Frequency table including zeros for unused values, on a data.table

问题描述

我有一个数据集如下：

library(data.table)

test <- data.table(structure(list(Issue.Date = structure(c(16041, 16056, 16042,15990, 15996, 16001, 15995, 15981, 15986, 15996, 15996, 16002,16015, 16020, 16025, 16032, 16023, 16084, 16077, 16102, 16104,16107, 16112, 16113, 16115, 16121, 16125, 16128, 16104, 16132,16133, 16135, 16139, 16146, 16151), class = "Date"), 
    Complaint = structure(c(1L,4L, 4L, 4L, 4L, 4L, 4L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 1L,5L, 3L, 1L, 3L, 1L, 4L, 4L, 3L, 3L, 3L, 3L, 3L, 2L, 2L, 1L, 3L,3L, 3L), .Label = c("A", "B", "C", "D", "E"), class = "factor"),
    yr = c("2013", "2013", "2013", "2013", "2013", "2013", "2013","2013", "2013", "2013", "2013", "2013", "2013", "2013", "2013","2013", "2013", "2014", "2014", "2014", "2014", "2014", "2014","2014", "2014", "2014", "2014", "2014", "2014", "2014", "2014","2014", "2014", "2014", "2014"), 
    Month = c("2013-12", "2013-12","2013-12", "2013-10", "2013-10", "2013-10", "2013-10", "2013-10","2013-10", "2013-10", "2013-10", "2013-10", "2013-11", "2013-11","2013-11", "2013-11", "2013-11", "2014-01", "2014-01", "2014-02","2014-02", "2014-02", "2014-02", "2014-02", "2014-02", "2014-02","2014-02", "2014-02", "2014-02", "2014-03", "2014-03", "2014-03","2014-03", "2014-03", "2014-03"), 
    da = c("02", "17", "03","12", "18", "23", "17", "03", "08", "18", "18", "24", "06","11", "16", "23", "14", "14", "07", "01", "03", "06", "11","12", "14", "20", "24", "27", "03", "03", "04", "06", "10","17", "22")), 
   .Names = c("Issue.Date", "Complaint", "yr","Month", "da"), class = c("data.table", "data.frame"), row.names = c(NA,-35L)))

基本上我想做的是使用 data.table 由月具有投诉和计数的频率表。诀窍是，如果没有投诉，那么我需要它显示一个 Count code> Month 。我知道如何做，不显示零，但我想知道如何包括它们。

Basically what I would like to do is use data.table to create a frequency table that has Complaint and Count by Month. The trick is that I need it to show a Count of zero if there are no Complaints of that type for that Month. I know how to do it without showing the zeros, but I want to know how to include them.

test[ , count := .N, by = "Month,Complaint"]

感谢任何帮助！

Thanks for any help!

推荐答案

要直接获取每个组的计数：

To directly get the counts for each group:

setkey(test, Month, Complaint)

# may need to also add allow.cartesian, depending on actual data
test[CJ(Month, Complaint, unique = TRUE), .N, by = .EACHI]
#      Month Complaint N
# 1: 2013-10         A 0
# 2: 2013-10         B 0
# 3: 2013-10         C 5
# 4: 2013-10         D 4
# 5: 2013-10         E 0
# 6: 2013-11         A 1
# 7: 2013-11         B 0
# 8: 2013-11         C 4
# 9: 2013-11         D 0
#10: 2013-11         E 0
#11: 2013-12         A 1
#12: 2013-12         B 0
#13: 2013-12         C 0
#14: 2013-12         D 2
#15: 2013-12         E 0
#16: 2014-01         A 0
#17: 2014-01         B 0
#18: 2014-01         C 1
#19: 2014-01         D 0
#20: 2014-01         E 1
#21: 2014-02         A 2
#22: 2014-02         B 0
#23: 2014-02         C 6
#24: 2014-02         D 2
#25: 2014-02         E 0
#26: 2014-03         A 1
#27: 2014-03         B 2
#28: 2014-03         C 3
#29: 2014-03         D 0
#30: 2014-03         E 0
#      Month Complaint N

如果您希望将计数放在完整的 data.table 中而不是汇总，请参见答案的第一个修订版。

See first revision of the answer if you want to have the counts in the full data.table instead of summarizing.

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