以组变量的总和为条件创建变量

Question

我有一个data.table，如下：

panelID = c(1:50)   
year    = c(2001:2010)
country = c("NLD", "BEL", "GER")
urban   = c("A", "B", "C")
indust  = c("D", "E", "F")
sizes   = c(1, 2, 3, 4, 5)
n <- 2

library(data.table)

set.seed(123)
DT <- data.table(
    panelID = rep(sample(panelID), each = n),
    country = rep(sample(country, length(panelID), replace = T), each = n),
    year    = c(replicate(length(panelID), sample(year, n))),
    some_NA = sample(0:5, 6),                                             
    some_NA_factor = sample(0:5, 6),
    industry       = rep(sample(indust, length(panelID), replace = T), each = n),
    urbanisation   = rep(sample(urban, length(panelID), replace = T), each = n),
    size      = rep(sample(sizes, length(panelID), replace = T), each = n),
    norm      = round(runif(100)/10, 2),
    sales     = round(rnorm(10, 10, 10), 2),
    Happiness = sample(10, 10),
    Sex       = round(rnorm(10, 0.75, 0.3), 2),
    Age       = sample(100, 100),
    Educ      = round(rnorm(10, 0.75, 0.3), 2)
)        
DT [, uniqueID := .I]  # Creates a unique ID     
DT[DT == 0] <- NA 
DT$sales[DT$sales< 0] <- NA 
DT <- as.data.frame(DT)

我想要的是panelIDs 的数量，其中size 的总和等于8。所以我想我会这样做：

DT[sum(size)==8, condition:=1, by=panelID]

我在这里做错了什么？

Answer 1

与data.table:

DT[,conditional:=ifelse(sum(size)==8,1,0),by=panelID][]
# To get the lengths of those which are True(1), save the above as res
#nrow(res[res[,conditional==1],"panelID"])

或者就像@chinsoon12 建议的那样：

DT[, conditional := +(sum(size)==8), panelID]

结果（头部）：

 panelID country year some_NA some_NA_factor industry urbanisation size norm sales
1:      31     GER 2010       4              1        F            C    4 0.09  5.63
2:      31     GER 2005       2             NA        F            C    4 0.03 13.31
3:      15     NLD 2005      NA              4        D            C    3 0.05    NA
4:      15     NLD 2008       1              5        D            C    3 0.01 12.12
5:      14     BEL 2003       5              3        E            B    1 0.09 22.37
6:      14     BEL 2002       3              2        E            B    1 0.04 30.38
   Happiness  Sex Age Educ uniqueID conditional
1:         7 0.69  62 0.25        1           1
2:         3 1.00  10 1.31        2           1
3:        10 0.66  59 0.73        3           0
4:         9 0.85  49 0.88        4           0
5:         2 0.34   7 0.90        5           0
6:         5 0.84  61 1.11        6           0

Answer 2

你可以用 dplyr 来做

你可以通过使用dplyr的这段代码来实现你想要的：

library(dplyr)
DT %>%
  group_by(panelID) %>%
  summarize(sum = sum(size)) %>%
  filter(sum == 8) %>%
  pull(panelID)

#Output
[1] 11 14 15 16 18 27 28 34 38 45

编辑

如果要显示面板数量，可以将pull(panelID)改成count()，或者在末尾加上lenght()，如下所示：

library(dplyr)
DT %>%
  group_by(panelID) %>%
  summarize(sum = sum(size)) %>%
  filter(sum == 8) %>%
  pull(panelID) %>%
  length()

#Output
[1] 10

希望这会有所帮助。

Answer 3

我刚刚删除了as.data.frame()。我使用连接将size 的总和与panelID 正确对齐。

我不明白的是，如果您想要满足总和给出的条件的panelID 的值，我猜是panelID。或者，如果您想要有多少 panelID（即个人？）满足条件。

在前一种情况下，你可以这样做：

panelID = c(1:50)   
year    = c(2001:2010)
country = c("NLD", "BEL", "GER")
urban   = c("A", "B", "C")
indust  = c("D", "E", "F")
sizes   = c(1, 2, 3, 4, 5)
n <- 2

library(data.table)

set.seed(123)
DT <- data.table(
  panelID = rep(sample(panelID), each = n),
  country = rep(sample(country, length(panelID), replace = T), each = n),
  year    = c(replicate(length(panelID), sample(year, n))),
  some_NA = sample(0:5, 6),                                             
  some_NA_factor = sample(0:5, 6),
  industry       = rep(sample(indust, length(panelID), replace = T), each = n),
  urbanisation   = rep(sample(urban, length(panelID), replace = T), each = n),
  size      = rep(sample(sizes, length(panelID), replace = T), each = n),
  norm      = round(runif(100)/10, 2),
  sales     = round(rnorm(10, 10, 10), 2),
  Happiness = sample(10, 10),
  Sex       = round(rnorm(10, 0.75, 0.3), 2),
  Age       = sample(100, 100),
  Educ      = round(rnorm(10, 0.75, 0.3), 2)
)        
DT [, uniqueID := .I]  # Creates a unique ID     
DT[DT == 0] <- NA 
DT$sales[DT$sales< 0] <- NA 

dt_sum = DT[ , .(size_sum = sum(size) ), by = panelID ]
setkey( dt_sum, panelID )
setkey( DT, panelID )

DT = DT[ dt_sum ]
final = DT[ size_sum == 8, .N, by = panelID ]
> final
    panelID N
 1:       6 2
 2:       8 2
 3:       9 2
 4:      11 2
 5:      18 2
 6:      22 2
 7:      28 2
 8:      30 2
 9:      31 2
10:      38 2

后一种情况，你只需统计final的行数：

> nrow( final )
6