[英]Matching elements of a list to a data frame using R
df is a data frame that contains ids, list is a list of attributes. df是一个包含ID的数据框, list是一个属性列表。 The first element of list contains the attributes for the first observation of df , and so on.
list的第一个元素包含df第一次观察的属性,依此类推。
How can I obtain a dataframe that matches ids with attributes? 如何获得将ID与属性匹配的数据框?
An example 一个例子
set.seed(1)
df= data.frame(id=paste(rep("id",10),1:10,sep=""))
list=replicate(10,letters[sample(1:26,sample(1:3,1),replace=T)])
head(df)
# id
# id1
# id2
# id3
# id4
# id5
head(list)
[[1]]
[1] "j"
[[2]]
[1] "x" "f"
[[3]]
[1] "y" "r" "q"
[[4]]
[1] "f"
[[5]]
[1] "r"
[[6]]
[1] "u" "m"
The first 5 observations of the resulting data frame should look like this 结果数据帧的前5个观察结果应如下所示
id attribute
1 id1 j
2 id2 x
3 id2 f
4 id3 y
5 id3 r
We can get the length
of each element of 'list' using lengths
(introduced in R 3.2.0
), replicate the 'df$id', unlist
the 'list' and create a 'data.frame' with those vectors. 我们可以得到的
length
使用“列表”中的每个元素的lengths
(以介绍R 3.2.0
),复制“DF的$ id”, unlist
的“名单”,并创建一个“data.frame”这些载体。
res <- data.frame(id=rep(df$id,lengths(list)), attribute=unlist(list))
head(res)
# id attribute
# 1 id1 j
# 2 id2 x
# 3 id2 f
# 4 id3 y
# 5 id3 r
# 6 id3 q
Or we can set the names of the 'list' with the 'id' column of the dataset ('df') and use stack
to get the long form 或者我们可以使用数据集的“ id”列(“ df”)设置“列表”的名称,并使用
stack
获取长格式
stack(setNames(list, df$id))
Or a similar approach with unnest
from tidyr
或用类似的方法
unnest
从tidyr
library(tidyr)
unnest(setNames(list, df$id), id)
NOTE: It is better not to name objects with a function name (in reference to 'list', 'df') 注意:最好不要使用函数名称来命名对象(参考“ list”,“ df”)
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