[英]R data.table to vector using variable name as data.table name?
I want to use a variable as the df name but cant figure out how.我想使用一个变量作为 df 名称,但不知道如何。 I can do it this way我可以这样做
'vector2 <- df$columname'
If i want to do it in a loop looking at different data tables i cant do it.如果我想循环查看不同的数据表,我不能这样做。 vector1 is the names of my data.tables that i want to put the column data into a vector2. vector1 是我想将列数据放入vector2 的data.tables 的名称。
I want the loop to do this我希望循环执行此操作
'vector2 <- one$columname'
'vector2 <- two$columname'
'vector2 <- three$columname'
changing the data.table name each time it goes through the loop keeping column name the same.每次通过循环保持列名相同时更改 data.table 名称。
'vector1<- c("one","two","three")
for(i in vector1) {
vector2 <- vector1$columname
}'
Based on the updated in OP's post, use either mget
(returns the values of all the objects into a named list) or get
(for a single element - can be used within for
loop) to return the values of the dataset names ie 'one', 'two', 'three'根据 OP 帖子中的更新,使用mget
(将所有对象的值返回到命名列表中)或get
(对于单个元素 - 可以在for
循环中使用)返回数据集名称的值,即'one ', '二三'
lst1 <- lapply(mget(vector1), function(x) x$columname)
If it should be a single vector如果它应该是单个向量
vector2 <- unlist(lst1)
In a for
loop, it can be done as在for
循环中,它可以完成为
for(i in vector1) vector2 <- get(i)$columname
This replaces 'vector2' in each iteration and gets the last columnname ie from 'three'.这将在每次迭代中替换“vector2”并获取最后一个列名,即来自“three”。 If we need to create a single vector如果我们需要创建单个向量
vector2 <- c()
for(i in vector1) vector2 <- c(vector2, get(i)$columname)
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