Question

我有一个csv文件，每个唯一ID有多行，我需要将其格式化为数据帧的单行。在阅读此文件后，我最终获得了一个初始数据框：

id  week   v1  v2
01  week1  3   2
01  week2  5   2
01  week3  2   3
02  week1  1   2
02  week2  5   5
03  week1  4   1
03  week2  4   3
03  week3  4   2
[etc...]

我想要为给定的id提取v1的所有实例，因此我抓住所有唯一ID

uniqid<-unique(data$id)

然后从1：length（uniqid）

迭代这些

temp <- subset(data,data$id==uniqid[i])

并将每周数据拉入临时变量

week1 <- temp$v1[temp$week=="week1]

所以我可以使用rbind

改造数据帧

output <- rbind(output,data.frame(ID=uniqid[i],week1,week2,week3))

我的问题是，例如id = 02，没有week3，所以rbind会中断。似乎永远不会创建week3变量;它没有显示为NA。如何测试变量是否已创建并将其设置为NA（或0）以便rbind不会失败？或者是否有完全不同/更有效的方法来实现这一目标？

Answer 1

您可以使用reshape2包中的recast功能。

DF
##   id  week v1 v2
## 1  1 week1  3  2
## 2  1 week2  5  2
## 3  1 week3  2  3
## 4  2 week1  1  2
## 5  2 week2  5  5
## 6  3 week1  4  1
## 7  3 week2  4  3
## 8  3 week3  4  2


require(reshape2)
temp <- recast(DF, id ~ week, measure.var = "v1")
result <- temp$data
row.names(result) <- temp$labels[[1]]$id
colnames(result) <- temp$labels[[2]]$week
result
##   week1 week2 week3
## 1     3     5     2
## 2     1     5    NA
## 3     4     4     4

或@AnandaMahto建议，只需使用dcast

dcast(DF, id ~ week, value.var = "v1")
##   id week1 week2 week3
## 1  1     3     5     2
## 2  2     1     5    NA
## 3  3     4     4     4

Answer 2

在基础R中，您可以使用reshape：

> reshape(mydf, direction = "wide", idvar="id", timevar="week")
  id v1.week1 v2.week1 v1.week2 v2.week2 v1.week3 v2.week3
1  1        3        2        5        2        2        3
4  2        1        2        5        5       NA       NA
6  3        4        1        4        3        4        2

如果要从输出中删除“v2”列，可以在重新整形数据之前执行此操作，也可以从函数中删除它。

> reshape(mydf, direction = "wide", idvar="id", timevar="week", drop="v2")
  id v1.week1 v1.week2 v1.week3
1  1        3        5        2
4  2        1        5       NA
6  3        4        4        4

将多个csv行读入R中的单行

2 个答案: