我正在尝试使用ifelse语句对我的数据表进行子集化，但我没有得到我正在寻找的结果。
我的初始数据表如下所示：
head(Data_copy, n = 18)
Company Date DOW variable value Year Month End_of_Month
1: ASXRI 1991-09-06 Friday RI NA 1991 Sep 0
2: ASXRI 1991-09-09 Monday RI NA 1991 Sep 0
3: ASXRI 1991-09-10 Tuesday RI NA 1991 Sep 0
4: ASXRI 1991-09-11 Wednesday RI NA 1991 Sep 0
5: ASXRI 1991-09-12 Thursday RI NA 1991 Sep 0
6: ASXRI 1991-09-13 Friday RI NA 1991 Sep 0
7: ASXRI 1991-09-16 Monday RI NA 1991 Sep 0
8: ASXRI 1991-09-17 Tuesday RI NA 1991 Sep 0
9: ASXRI 1991-09-18 Wednesday RI NA 1991 Sep 0
10: ASXRI 1991-09-19 Thursday RI NA 1991 Sep 0
11: ASXRI 1991-09-20 Friday RI NA 1991 Sep 0
12: ASXRI 1991-09-23 Monday RI NA 1991 Sep 0
13: ASXRI 1991-09-24 Tuesday RI NA 1991 Sep 0
14: ASXRI 1991-09-25 Wednesday RI NA 1991 Sep 0
15: ASXRI 1991-09-26 Thursday RI NA 1991 Sep 0
16: ASXRI 1991-09-27 Friday RI NA 1991 Sep 0
17: ASXRI 1991-09-30 Monday RI NA 1991 Sep 1
18: ASXRI 1991-10-01 Tuesday RI NA 1991 Oct 0
这是250,000中的18行。
我想要的是基于ifelse函数拆分此数据表，如下所示：
Data1 <- ifelse("Weekly" == "Weekly", Data_copy[End_of_Month ==1,], Data_copy)
*“Weekly”==“Weekly”位将在稍后的函数中使用。
我希望Data1是一个新的数据表，它只包含End_of_Month == 1的行。
当我运行上面的代码时，我发现我得到了公司名称的列表，就是这样。
我会告诉你输出的样子：
Data1[[1]]
[1] "ASXRI" "ASXRI" "ASXRI" "ASXRI" "ASXRI" "ASXRI" "ASXRI" "ASXRI" "ASXRI" "ASXRI" "ASXRI"
现在如果我向下滚动，我得到：
[1387] "AANRI" "AANRI" "AANRI" "AANRI" "AANRI" "AANRI" "APARI" "APARI" "APARI" "APARI" "APARI"
[1398] "APARI" "APARI" "APARI" "APARI" "APARI" "APARI" "APARI" "APARI" "APARI" "APARI" "APARI"
这些条目中的每一个都只是公司名称之一。
如果我这样做，我会得到我想要的结果：
Data2 <- Data_copy[End_of_Month == 1, ]
Company Date DOW variable value Year Month End_of_Month
1: ASXRI 1991-09-30 Monday RI NA 1991 Sep 1
2: ASXRI 1991-10-31 Thursday RI NA 1991 Oct 1
3: ASXRI 1991-11-29 Friday RI NA 1991 Nov 1
4: ASXRI 1991-12-31 Tuesday RI NA 1991 Dec 1
5: ASXRI 1992-01-31 Friday RI NA 1992 Jan 1
6: ASXRI 1992-02-28 Friday RI NA 1992 Feb 1
基本上我想复制Data2，但是使用ifelse语句。
这是前100行：
dput(head(Data_copy, n = 100))
structure(list(Company = c("ASXRI", "ASXRI", "ASXRI", "ASXRI",
"ASXRI", "ASXRI", "ASXRI", "ASXRI", "ASXRI", "ASXRI", "ASXRI",
"ASXRI", "ASXRI", "ASXRI", "ASXRI", "ASXRI", "ASXRI", "ASXRI",
"ASXRI", "ASXRI", "ASXRI", "ASXRI", "ASXRI", "ASXRI", "ASXRI",
"ASXRI", "ASXRI", "ASXRI", "ASXRI", "ASXRI", "ASXRI", "ASXRI",
"ASXRI", "ASXRI", "ASXRI", "ASXRI", "ASXRI", "ASXRI", "ASXRI",
"ASXRI", "ASXRI", "ASXRI", "ASXRI", "ASXRI", "ASXRI", "ASXRI",
"ASXRI", "ASXRI", "ASXRI", "ASXRI", "ASXRI", "ASXRI", "ASXRI",
"ASXRI", "ASXRI", "ASXRI", "ASXRI", "ASXRI", "ASXRI", "ASXRI",
"ASXRI", "ASXRI", "ASXRI", "ASXRI", "ASXRI", "ASXRI", "ASXRI",
"ASXRI", "ASXRI", "ASXRI", "ASXRI", "ASXRI", "ASXRI", "ASXRI",
"ASXRI", "ASXRI", "ASXRI", "ASXRI", "ASXRI", "ASXRI", "ASXRI",
"ASXRI", "ASXRI", "ASXRI", "ASXRI", "ASXRI", "ASXRI", "ASXRI",
"ASXRI", "ASXRI", "ASXRI", "ASXRI", "ASXRI", "ASXRI", "ASXRI",
"ASXRI", "ASXRI", "ASXRI", "ASXRI", "ASXRI"), Date = structure(c(7918,
7921, 7922, 7923, 7924, 7925, 7928, 7929, 7930, 7931, 7932, 7935,
7936, 7937, 7938, 7939, 7942, 7943, 7944, 7945, 7946, 7949, 7950,
7951, 7952, 7953, 7956, 7957, 7958, 7959, 7960, 7963, 7964, 7965,
7966, 7967, 7970, 7971, 7972, 7973, 7974, 7977, 7978, 7979, 7980,
7981, 7984, 7985, 7986, 7987, 7988, 7991, 7992, 7993, 7994, 7995,
7998, 7999, 8000, 8001, 8002, 8005, 8006, 8007, 8008, 8009, 8012,
8013, 8014, 8015, 8016, 8019, 8020, 8021, 8022, 8023, 8026, 8027,
8028, 8029, 8030, 8033, 8034, 8035, 8036, 8037, 8040, 8041, 8042,
8043, 8044, 8047, 8048, 8049, 8050, 8051, 8054, 8055, 8056, 8057
), class = "Date"), DOW = c("Friday", "Monday", "Tuesday", "Wednesday",
"Thursday", "Friday", "Monday", "Tuesday", "Wednesday", "Thursday",
"Friday", "Monday", "Tuesday", "Wednesday", "Thursday", "Friday",
"Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Monday",
"Tuesday", "Wednesday", "Thursday", "Friday", "Monday", "Tuesday",
"Wednesday", "Thursday", "Friday", "Monday", "Tuesday", "Wednesday",
"Thursday", "Friday", "Monday", "Tuesday", "Wednesday", "Thursday",
"Friday", "Monday", "Tuesday", "Wednesday", "Thursday", "Friday",
"Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Monday",
"Tuesday", "Wednesday", "Thursday", "Friday", "Monday", "Tuesday",
"Wednesday", "Thursday", "Friday", "Monday", "Tuesday", "Wednesday",
"Thursday", "Friday", "Monday", "Tuesday", "Wednesday", "Thursday",
"Friday", "Monday", "Tuesday", "Wednesday", "Thursday", "Friday",
"Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Monday",
"Tuesday", "Wednesday", "Thursday", "Friday", "Monday", "Tuesday",
"Wednesday", "Thursday", "Friday", "Monday", "Tuesday", "Wednesday",
"Thursday", "Friday", "Monday", "Tuesday", "Wednesday", "Thursday"
), variable = structure(c(1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L,
1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L,
1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L,
1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L,
1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L,
1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L,
1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L), .Label = c("RI",
"VO", "MV", "TD", "ND"), class = "factor"), value = c(NA_real_,
NA_real_, NA_real_, NA_real_, NA_real_, NA_real_, NA_real_, NA_real_,
NA_real_, NA_real_, NA_real_, NA_real_, NA_real_, NA_real_, NA_real_,
NA_real_, NA_real_, NA_real_, NA_real_, NA_real_, NA_real_, NA_real_,
NA_real_, NA_real_, NA_real_, NA_real_, NA_real_, NA_real_, NA_real_,
NA_real_, NA_real_, NA_real_, NA_real_, NA_real_, NA_real_, NA_real_,
NA_real_, NA_real_, NA_real_, NA_real_, NA_real_, NA_real_, NA_real_,
NA_real_, NA_real_, NA_real_, NA_real_, NA_real_, NA_real_, NA_real_,
NA_real_, NA_real_, NA_real_, NA_real_, NA_real_, NA_real_, NA_real_,
NA_real_, NA_real_, NA_real_, NA_real_, NA_real_, NA_real_, NA_real_,
NA_real_, NA_real_, NA_real_, NA_real_, NA_real_, NA_real_, NA_real_,
NA_real_, NA_real_, NA_real_, NA_real_, NA_real_, NA_real_, NA_real_,
NA_real_, NA_real_, NA_real_, NA_real_, NA_real_, NA_real_, NA_real_,
NA_real_, NA_real_, NA_real_, NA_real_, NA_real_, NA_real_, NA_real_,
NA_real_, NA_real_, NA_real_, NA_real_, NA_real_, NA_real_, NA_real_,
NA_real_), Year = c("1991", "1991", "1991", "1991", "1991", "1991",
"1991", "1991", "1991", "1991", "1991", "1991", "1991", "1991",
"1991", "1991", "1991", "1991", "1991", "1991", "1991", "1991",
"1991", "1991", "1991", "1991", "1991", "1991", "1991", "1991",
"1991", "1991", "1991", "1991", "1991", "1991", "1991", "1991",
"1991", "1991", "1991", "1991", "1991", "1991", "1991", "1991",
"1991", "1991", "1991", "1991", "1991", "1991", "1991", "1991",
"1991", "1991", "1991", "1991", "1991", "1991", "1991", "1991",
"1991", "1991", "1991", "1991", "1991", "1991", "1991", "1991",
"1991", "1991", "1991", "1991", "1991", "1991", "1991", "1991",
"1991", "1991", "1991", "1991", "1991", "1992", "1992", "1992",
"1992", "1992", "1992", "1992", "1992", "1992", "1992", "1992",
"1992", "1992", "1992", "1992", "1992", "1992"), Month = c("Sep",
"Sep", "Sep", "Sep", "Sep", "Sep", "Sep", "Sep", "Sep", "Sep",
"Sep", "Sep", "Sep", "Sep", "Sep", "Sep", "Sep", "Oct", "Oct",
"Oct", "Oct", "Oct", "Oct", "Oct", "Oct", "Oct", "Oct", "Oct",
"Oct", "Oct", "Oct", "Oct", "Oct", "Oct", "Oct", "Oct", "Oct",
"Oct", "Oct", "Oct", "Nov", "Nov", "Nov", "Nov", "Nov", "Nov",
"Nov", "Nov", "Nov", "Nov", "Nov", "Nov", "Nov", "Nov", "Nov",
"Nov", "Nov", "Nov", "Nov", "Nov", "Nov", "Dec", "Dec", "Dec",
"Dec", "Dec", "Dec", "Dec", "Dec", "Dec", "Dec", "Dec", "Dec",
"Dec", "Dec", "Dec", "Dec", "Dec", "Dec", "Dec", "Dec", "Dec",
"Dec", "Jan", "Jan", "Jan", "Jan", "Jan", "Jan", "Jan", "Jan",
"Jan", "Jan", "Jan", "Jan", "Jan", "Jan", "Jan", "Jan", "Jan"
), End_of_Month = c(0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0)), .Names = c("Company", "Date", "DOW", "variable", "value",
"Year", "Month", "End_of_Month"), class = c("data.table", "data.frame"
), row.names = c(NA, -100L), .internal.selfref = <pointer: 0x00000000001f0788>)
答案 0 :(得分：2)
其他用户注意到ifelse不适合您的目的。解释原因可能很有用。从?ifelse开始，ifelse(test, yes, no)会返回
相同长度和属性的矢量（包括尺寸 和'＆＃34; class＆＃34;'）作为'测试'和来自'是'值的数据值 或'不'
换句话说，如果您的test向量的长度为1，则ifelse(...)将返回长度为1的向量。例如，
> ifelse(TRUE, 1:3, 7:9)
[1] 1
> ifelse(c(TRUE, FALSE), 1:3, 7:9)
[1] 1 8
在你的情况下，
ifelse("Weekly" == "Weekly", Data_copy[End_of_Month ==1,], Data_copy)
将返回长度为1的向量。更准确地说，由于测试返回TRUE，ifelse将返回yes参数中的第一个元素;因为它是一个数据帧（一种列表），ifelse返回数据帧的第一个元素，即第一列。这就是您获得公司名称列表的原因。如果您真的想使用ifelse构造，请尝试
ifelse("Weekly" == "Weekly", list(Data_copy[End_of_Month ==1,]), list(Data_copy))
虽然正如其他人所说，但最好不要使用if {} else {}。