R - 替换矢量列表中的元素

Question

我有矢量列表，并且想要将矢量指定给它的一个位置（覆盖）。以下是示例代码：

for (nodeId in names(chains)) { 
    chains[nodeId] <- unlist(chains[nodeId])[-1] 
} 

分配后我收到许多警告，告诉我列表长度不相等。我明白，发生的任务不是我想要的。

有什么办法可以用unlist(chains[nodeId])[-1]代替chains[nodeId]中的元素吗？

当我做str(chains)，str(chains[nodeId])和str(unlist(chains[nodeId])[-1])我获得以下的输出：

$str(chains) 
List of 15 
$ 4 : chr [1:3] "root" "alcohol< 9.85" "totalSulfurDioxide>=60.5" 
$ 10 : chr [1:4] "root" "alcohol< 9.85" "totalSulfurDioxide< 60.5" "sulphates< 0.575" 
$ 22 : chr [1:5] "root" "alcohol< 9.85" "totalSulfurDioxide< 60.5" "sulphates>=0.575" ... 
(...) lots more 

$str(chains[nodeId]) 
List of 1 
$ 4: chr [1:3] "root" "alcohol< 9.85" "totalSulfurDioxide>=60.5" 

$str(unlist(chains[nodeId])[-1]) 
Named chr [1:2] "alcohol< 9.85" "totalSulfurDioxide>=60.5" 
- attr(*, "names")= chr [1:2] "42" "43" 

更新：str替换dput;加入dput(chains[nodeId])

$ dput(chains) 
structure(list(`4` = "alcohol< 9.85", `10` = "alcohol< 9.85", 
    `22` = "alcohol< 9.85", `92` = "alcohol< 9.85", `93` = "alcohol< 9.85", 
    `47` = "alcohol< 9.85", `24` = "alcohol>=9.85", `50` = "alcohol>=9.85", 
    `102` = "alcohol>=9.85", `103` = "alcohol>=9.85", `26` = "alcohol>=9.85", 
    `27` = "alcohol>=9.85", `28` = "alcohol>=9.85", `29` = "alcohol>=9.85", 
    `15` = c("root", "alcohol>=9.85", "alcohol>=11.55", "sulphates>=0.685" 
    )), .Names = c("4", "10", "22", "92", "93", "47", "24", "50", 
"102", "103", "26", "27", "28", "29", "15")) 

$ dput(chains[nodeId]) 
structure(list(`15` = c("root", "alcohol>=9.85", "alcohol>=11.55", 
"sulphates>=0.685")), .Names = "15") 

$ dput(unlist(chains[nodeId])[-1)) 
structure(c("alcohol>=9.85", "alcohol>=11.55", "sulphates>=0.685" 
), .Names = c("152", "153", "154")) 

$ dput(chains[nodeId]) 
structure(list(`15` = "alcohol>=9.85"), .Names = "15") 

我想实现的是从向量中删除第一个元素锁链[NODEID]

Answer 1

如果chains是列表，nodeId是一个字符串，然后chains[nodeId]将名单长一个。您需要chains[[nodeId]]，其中包含该列表的内容。

Answer 2

这是你想要的吗？

# make a list of vectors since no data provided 
origlist<-lapply(1:3,function(x)c("a",paste0("b",x),"c")) 
names(origlist)<-c("_1","_2","_3") 

$`_1` 
[1] "a" "b1" "c" 

$`_2` 
[1] "a" "b2" "c" 

$`_3` 
[1] "a" "b3" "c" 

# remove first item from each as per your example 
lapply(origlist, tail, n = -1) 

$`_1` 
[1] "b1" "c" 

$`_2` 
[1] "b2" "c" 

$`_3` 
[1] "b3" "c"