[英]R Transformation Collapsing Rows
I would like to take a data frame and collapse the rows on a column and simply create another column that is a vector of all the values. 我想获取一个数据框并折叠列上的行,然后简单地创建另一列,该列是所有值的向量。
For example I would like to transform a data frame like this: 例如,我想像这样转换一个数据框:
id item
1 100
1 103
1 109
1 101
2 102
2 109
2 107
2 105
3 105
3 106
3 101
3 102
3 110
To: 至:
id item
1 (100,103,109,101)
2 (102,109,107,105)
3 (105,106,101,102,110)
So the first column is the unique id and the second column is a vector/list of all the items that were seen for that id. 因此,第一列是唯一ID,第二列是针对该ID看到的所有项目的向量/列表。 Seems like this should be easy but I haven't been able to find a solution. 似乎这样应该很容易,但我一直找不到解决方案。 As noted in the example the amount of items can vary per id. 如示例中所述,每个id的商品数量可能有所不同。
Here is code to create the initial data frame I am trying to transform. 这是用于创建我要转换的初始数据帧的代码。
id <- c(1,1,1,1,2,2,2,2,3,3,3,3,3)
item <- c(100,103,109,101,102,109,107,105,105,106,101,102,110)
input_frame <- data.frame(cbind(id,item))
You can use aggregate
function to group by id and then collect the respective elements from item using c
function: 您可以使用aggregate
函数按ID分组,然后使用c
函数从item收集各个元素:
aggregate(formula = item ~ id, data = input_frame, FUN = c)
Output: 输出:
id item
1 1 100, 103, 109, 101
2 2 102, 109, 107, 105
3 3 105, 106, 101, 102, 110
library (plyr)
ddply(input_frame,.(id),summarize,val=paste(item,collapse=","))
id val
1 1 100,103,109,101
2 2 102,109,107,105
3 3 105,106,101,102,110
This is a solution that produces a nested list: 这是产生嵌套列表的解决方案:
item_list <- lapply(unique(id), function(i)
list(id=i,item=input_frame$item[id==i]) )
You can access the items for, say, id==2
by 您可以通过以下方式访问id==2
的项目
item_list[[2]]$item
library(dplyr)
summarise(group_by(input_frame,id),item=paste(item,collapse=','))
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