r - R中dcast的一个特例

Question

我的问题似乎很简单，而且我确实为我无法让它发挥作用而感到非常恼火。假设我有一个简单dataframe的一列 forgroup和一个 variable x。因为我的变量组包含一个“控制”条件，所以我想t.test针对我的控制变量运行所有其他条件。

library(data.table) # I am use to the data.table sintax, tho I will happily accept a solution in any other dialect

# Generate dummy data
set.seed(1)
 df <- data.table(x = rnorm(100), g = sample(LETTERS[1:3], size = 100, replace =T ))
setkey(df, g, x) # Order

 df # Inspect data

为此，我想dcast控制组并将其添加为新列。由于我想要运行 t 检验，因此我将使用整个组，我不介意该列的包含顺序。但是，我用来从长格式更改为宽格式 ( dcast) 的功能在这里似乎不起作用。

# dcast appoach
m <- dcast(df, x ~ g) # This is just... B*#!!it

所以这是我寻找的近似值：

# Kind of what I want

# Isolate control condition
Control <- df[g == "C"] 

df[, C := rep(Control, 3)] # In this case it says there a "remainder", tho I would prefer to add NAs to the variable x until completion

我也不介意将所有组 A、B 和 C 作为列。

在此先感谢您的帮助

Answer 1

也许，这可能是 OP 所要求的：

library(data.table)
dcast(df, rowid(g) ~ g, value.var = "x")

     g            A           B           C
 1:  1 -1.804958629 -1.98935170 -2.21469989
 2:  2 -1.470752384 -1.52356680 -0.74327321
 3:  3 -1.276592208 -1.37705956 -0.62124058
 4:  4 -1.253633400 -1.12936310 -0.61202639
 5:  5 -1.224612615 -1.04413463 -0.58952095
 6:  6 -0.934097632 -0.83562861 -0.47340064
 7:  7 -0.709946431 -0.82046838 -0.41499456
 8:  8 -0.707495157 -0.68875569 -0.39428995
 9:  9 -0.626453811 -0.47815006 -0.30538839
10: 10 -0.573265414 -0.25336168 -0.13505460
11: 11 -0.568668733 -0.13517862  0.02800216
12: 12 -0.542520031 -0.11234621  0.39810588
13: 13 -0.443291873 -0.05931340  0.41794156
14: 14 -0.367221476 -0.05612874  0.55848643
15: 15 -0.304183924 -0.05380504  0.61982575
16: 16 -0.164523596 -0.01619026  0.69696338
17: 17 -0.155795507  0.07434132  0.82122120
18: 18 -0.102787727  0.15325334  0.88110773
19: 19 -0.044933609  0.34111969  0.94383621
20: 20 -0.039240003  0.36458196  1.12493092
21: 21  0.001105352  0.38767161  1.16040262
22: 22  0.074564983  0.48742905  1.17808700
23: 23  0.183643324  0.56971963  1.46555486
24: 24  0.188792300  0.59390132  1.51178117
25: 25  0.267098791  0.61072635          NA
26: 26  0.291446236  0.76317575          NA
27: 27  0.329507772  1.10002537          NA
28: 28  0.332950371  1.35867955          NA
29: 29  0.370018810  1.43302370          NA
30: 30  0.389843236  1.58683345          NA
31: 31  0.475509529  2.40161776          NA
32: 32  0.556663199          NA          NA
33: 33  0.575781352          NA          NA
34: 34  0.593946188          NA          NA
35: 35  0.689739362          NA          NA
36: 36  0.700213650          NA          NA
37: 37  0.738324705          NA          NA
38: 38  0.768532925          NA          NA
39: 39  0.782136301          NA          NA
40: 40  0.918977372          NA          NA
41: 41  1.063099837          NA          NA
42: 42  1.207867806          NA          NA
43: 43  1.595280802          NA          NA
44: 44  1.980399899          NA          NA
45: 45  2.172611670          NA          NA
     g            A           B           C

这是通过人为rowid(g)地为每个组引入单独的行数来实现的。

但是，根据42- 的评论，我不明白这将如何帮助解决 OP 的潜在问题。