投，加入和减少重塑

Question

数据我有一个数据帧，看起来像

MAP name  series ID 
1.0 aspartame baseline 902349 
1.0 aspartame baseline 82749 
1.0 aspartame baseline 928542 
1.0 aspartame next  928542 
0.8 aspartame next  82749 
0.8 aspartame next  902349 

而且我想加入的ID这些数据，并计算基准，并在接下来的MAP之间的差异 得分了。所以这应该给

diff name  ID 
0.2 aspartame 902349 
0.2 aspartame 82749 
0.0 aspartame 928542 

Answer 1

按照要求通过OP ：使用reshape（或更确切地说reshape2）的解决方案。

d <- read.table(text = " 
MAP name  series ID 
1.0 aspartame baseline 902349 
1.0 aspartame baseline 82749 
1.0 aspartame baseline 928542 
1.0 aspartame next  928542 
0.8 aspartame next  82749 
0.8 aspartame next  902349", header = TRUE) 

require(reshape2) 

dcast(data = d, formula = ID + name~ ., value.var = "MAP", 
     fun.aggregate = function(x) (x[1] - x[2])) 

给

 ID  name NA 
1 82749 aspartame 0.2 
2 902349 aspartame 0.2 
3 928542 aspartame 0.0 

Answer 2

这里是基础R的方式（假设你的data.frame名为df）：

aggregate(list(MAP = df$MAP), 
      by=list(ID = df$ID, name = df$name), 
      function(x) x[1] - x[2]) 
#  ID  name MAP 
# 1 82749 aspartame 0.2 
# 2 902349 aspartame 0.2 
# 3 928542 aspartame 0.0 

Answer 3

你可以使用plyr：

library(plyr) 
ddply(your_data, c("ID", "name"), 
     function(df){subset(df, series == "baseline", select = "MAP")- 
     subset(df, series == "next", select = "MAP")})