在数据框中按组折叠文本 [英] Collapse text by group in data frame
本文介绍了在数据框中按组折叠文本的处理方法,对大家解决问题具有一定的参考价值,需要的朋友们下面随着小编来一起学习吧!
问题描述
如何在 group
列中按组聚合数据框并在 text
列中折叠文本?
How do I aggregate data frame by group in column group
and collapse text in column text
?
示例数据:
df <- read.table(header=T, text="
group text
a a1
a a2
a a3
b b1
b b2
c c1
c c2
c c3
")
所需的输出(数据框):
Required output (data frame):
group text
a a1a2a3
b b1b2
c c1c2c3
现在我有:
sapply(unique(df$group), function(x) {
paste0(df[df$group==x,"text"], collapse='')
})
这在某种程度上有效,因为它返回按组正确折叠的文本,但作为向量:
This works to some extent as it returns text properly collapsed by group, but as a vector:
[1] "a1a2a3" "b1b2" "c1c2c3"
我需要一个带有 group
列的数据框.
I need a data frame with group
column as a result.
推荐答案
只需使用 aggregate
:
aggregate(df$text, list(df$group), paste, collapse="")
## Group.1 x
## 1 a a1a2a3
## 2 b b1b2
## 3 c c1c2c3
或使用 plyr
library(plyr)
ddply(df, .(group), summarize, text=paste(text, collapse=""))
## group text
## 1 a a1a2a3
## 2 b b1b2
## 3 c c1c2c3
如果数据集很大,
ddply
比 aggregate
快.
ddply
is faster than aggregate
if you have a large dataset.
编辑:根据@SeDur 的建议:
EDIT : With the suggestion from @SeDur :
aggregate(text ~ group, data = df, FUN = paste, collapse = "")
## group text
## 1 a a1a2a3
## 2 b b1b2
## 3 c c1c2c3
对于与之前的方法相同的结果,您必须这样做:
For the same result with earlier method you have to do :
aggregate(x=list(text=df$text), by=list(group=df$group), paste, collapse="")
EDIT2 :使用 data.table
:
library("data.table")
dt <- as.data.table(df)
dt[, list(text = paste(text, collapse="")), by = group]
## group text
## 1: a a1a2a3
## 2: b b1b2
## 3: c c1c2c3
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