[英]Extract data from list of lists [R]
I have a list of lists (mydata$notes) that I want to extract data from. 我有一个列表(mydata $ notes),我想从中提取数据。 Code looks like this, if I want to extract "location" - this works fine.
代码看起来像这样,如果我想提取“位置” - 这很好。
location <- unlist (lapply(mydata$notes, function(e) e$location))
Now, I might have more variables I want to extract, say a vector of 20, "location", "var1", "var2", "var3" and so on, in an atomic vector 现在,我可能有更多我想要提取的变量,例如20的矢量,“位置”,“var1”,“var2”,“var3”等等,在原子矢量中
names(unlist(mytree$notes[[1]]))
How can I loop my first code to extract all variables given in this names-variable? 如何循环我的第一个代码来提取这个名称变量中给出的所有变量?
Cheers 干杯
Define a vector to hold the list elements which you want to extract. 定义一个向量来保存要提取的列表元素。 Then call
unlist()
on each list which is processed by your call to lapply()
. 然后在每个列表上调用
unlist()
,该列表由您调用lapply()
。
vars <- c("location", "var1", "var2", "var3")
location <- unlist (lapply(mydata$notes,
function(e) {
unlist(e[vars])
}))
Notice that the only real change I made is that instead of returning the atomic vector e$location
I instead return a vector consisting of several collapsed elements from each list. 请注意,我所做的唯一真正的改变是,不是返回原子向量
e$location
而是返回一个由每个列表中的几个折叠元素组成的向量。
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