r-检查一个数据帧的给定id在另一个数据框中是否存在特定值

Question

我有两个数据帧"a"one_answers"b"。

str(a)
'data.frame':   1597 obs. of  2 variables:
 $ id : int  ...
 $ age: num  ...
> str(b)
'data.frame':   12877 obs. of  2 variables:
 $ id      : int  ...
 $ code    : chr  ...

虽然"id"在"a"中是唯一的，但在"b"中不是唯一的。更准确地说，"a"one_answers"b"之间存在1:n的关系。我想检查"a$id"的"b"中是否有特定代码。我该怎么做？

我想，我需要这样的东西：

a$code.I25 <- ifelse(<if there is a$id in b$id and for b$id an entry with "I25" for b$code>, 1, 0)

不幸的是，它有点复杂。"b$code"的值不仅像"I25"，而且更像"I25.11"或"I25.12"。然而，我只想比较"I25"，并想得到两者的真值，"I25.11"one_answers"I25.12"。这可能吗？

Answer 1

#create a dummy data.frame for a 
foo.a <- data.frame(id = 1:20,age = rnorm(20,25))
foo.b <-data.frame(id = 1:40,
code = as.character(paste(c("I25","I27"),1:20,sep = ".")))
#replicate it randomly
set.seed(357)
foo.b <-foo.b[sample(nrow(foo.b),75, replace = T),]
#check for matches
id.match <-which(foo.b$id %in% foo.a$id)
#get matching rows
foo.b[grep("I25",foo.b$code[id.match]),]

Answer 2

下面是一个示例

id_a = c(1, 2, 3, 23, 19, 11:13, 4, 6)
id_b = c(1, 2, 2, 5, 8, 11:13, 3, 3)
code_b = c(rep("I25", 4), rep("I26", 5), "I25")
a = data.frame(id = id_a, stringsAsFactors = FALSE)
a
#    id
# 1   1
# 2   2
# 3   3
# 4  23
# 5  19
# 6  11
# 7  12
# 8  13
# 9   4
# 10  6
b = data.frame(id = id_b, code = code_b, stringsAsFactors = FALSE)
b
#    id code
# 1   1  I25
# 2   2  I25
# 3   2  I25
# 4   5  I25
# 5   8  I26
# 6  11  I26
# 7  12  I26
# 8  13  I26
# 9   3  I26
# 10  3  I25
index = which(b$id %in% a$id)
b[index[which(b[index,]$code %in% "I25")],]
# id code
# 1   1  I25
# 2   2  I25
# 3   2  I25
# 10  3  I25
b[index[which(b[index,]$code %in% c("I25", "I26"))],]
#    id code
# 1   1  I25
# 2   2  I25
# 3   2  I25
# 6  11  I26
# 7  12  I26
# 8  13  I26
# 9   3  I26
# 10  3  I25

#真|假

b$TF = rep(NA, nrow(b))
b$TF[index[which(b[index,]$code %in% c("I25", "I26"))]] <- 1
b$TF[-(index[which(b[index,]$code %in% c("I25", "I26"))])] <- 0
b
#    id code TF
# 1   1  I25  1
# 2   2  I25  1
# 3   2  I25  1
# 4   5  I25  0
# 5   8  I26  0
# 6  11  I26  1
# 7  12  I26  1
# 8  13  I26  1
# 9   3  I26  1
# 10  3  I25  1