dataframe中如何得到

dataframe  v1 v2
a   1
b   1
b   2
c   2
c   3
c   4
如何得到
v1 v2
a    1
b    1
      2
c    2
      3
      4

谢谢！

1. A1 <- data.frame(v1=rep(c('a','b','c'),1:3),v2=c(1,1,2,2,3,4))
   
2. rn <- as.numeric(unlist(lapply(split(A1,A1$v1),function(x) rownames(x[1,]))))
   
3. A1$v1 <- 'NA'
   
4. A1$v1[rn] <- as.factor(c('a','b','c'))
   
5. A1

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https://bbs.pinggu.org/thread-2515424-1-1.html

1. a="sex"
   
2. b=matrix(1:2,nrow=2)
   
3. rownames(b) <- c(a,"")
   
4. colnames(b)<-""
   
5. b

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比较起以上仁兄的matrix，似乎太多步骤了...

ryusukekenji 发表于 2013-7-5 00:43
https://bbs.pinggu.org/thread-2515424-1-1.html
比较起以上仁兄的matrix，似乎太多步骤了...{:soso_e14 ...

如果v1 的取值很多，
这样写A1$v1[rn] <- as.factor(c('a','b','c')) 很麻烦啊

Suppose the variable "v1" is of type character:

1. A1 <- data.frame(v1=rep(c('a','b','c'),1:3),v2=c(1,1,2,2,3,4), stringsAsFactors = F)
   
2. 
   
3. with(A1, data.frame(v1 = do.call(c, lapply(split(v1, v1), function(cv) c(unique(cv), rep("", length = length(cv) - 1)))), v2 = v2, row.names = NULL))

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1. > x1 <- c("a","b","b","c","c","c")
   
2. > x2 <- c(1,1,2,2,3,4)
   
3. > a <- match(c("a","b","c"),x1)
   
4. >
   
5. > x1[-a] <- ""
   
6. >
   
7. > x <- data.frame(x1, x2)
   
8. > x
   
9.   x1 x2
   
10. 1  a  1
    
11. 2  b  1
    
12. 3     2
    
13. 4  c  2
    
14. 5     3
    
15. 6     4
    
16. >

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