列Mean by因子

Question

我想创建一个按应变系数列平均值的表

我有以下数据：

    Age Strain            103             3           163            39
V2   28  101CD  -3.4224173012 -0.3360570164 -9.2417448649 -3.6094766494
V3   28  101CD  -3.6487198656 -0.7948262475 -4.6350611123 -1.9232938265
V4   28  101CD  -7.0936427264 -0.1981243536 -9.2063428591  -3.367139071
V5   28  101CD  -5.9245254437 -0.1161875584 -7.3830396092 -4.7980771085
V6   30 101HFD  -9.4618204696 -5.0355557149 -3.9915005349 -0.9271933496
V7   30 101HFD   -8.805867863  -2.667103793 -2.2489197384 -1.5169130813
V8   30 101HFD -10.9841335945 -2.9617657815 -3.3460597574  -1.121806194
V9   30 101HFD -10.4612747952 -4.3759351258 -4.4322637085  -0.772499965
V10  30 101HFD  -9.2871507889 -1.2664335711 -4.3142098012 -1.3791233817
V11  30 101HFD -10.9443983294 -2.4651954898 -4.7759052834 -1.0954401254
V12  29  103CD  -2.7492530803 -2.0659306194 -2.5698186069 -1.4978280502
V13  29  103CD  -6.4401905692 -2.1098420514 -3.4349220483 -0.8836564768
V14  29  103CD   -6.479929929 -2.4792621691  -3.368774934 -0.7756932376
V15  29  103CD  -3.6586850957 -1.9145944032 -3.0911223702 -1.2730896376
V16  29  103CD  -7.1377230731  -1.413139617 -2.9203340711 -1.3152010161
V17  29 103HFD  -9.4624093184 -1.3265834556 -4.1871313168 -1.0108235293
V18  29 103HFD   -7.336764023 -0.8712499419  -4.204313727 -1.4450582002
V19  29 103HFD   -7.036723106 -0.7546877382 -6.0432957599 -1.4161366956
V20  29 103HFD  -9.4449207581 -0.9226067311 -4.6305567775  -1.320094489
V21  29 103HFD  -9.6383454033 -1.9620356763 -3.0214290407 -0.8602682738

最后，我想用这个来结束：

    Age Strain            103             3           163            39
V1  28   101CD  -3.4224173012 -0.3360570164 -9.2417448649 -3.6094766494
V2  30  101HFD  -9.4618204696 -5.0355557149 -3.9915005349 -0.9271933496
V3  29   103CD  -2.7492530803 -2.0659306194 -2.5698186069 -1.4978280502
V4  29  103HFD  -9.4624093184 -1.3265834556 -4.1871313168 -1.0108235293

其中1是具有Strain=101CD的所有样本的所有列的平均值，2:3是具有Strain=101HFD的样本的所有列的平均值，依此类推。

我尝试使用：

> ave <- aggregate(data, as.list(factor(data$Age)), mean)
Error in aggregate.data.frame(data, as.list(factor(data$Age)), mean) : arguments must have same length

和

> ave <- sapply(split(data, data$Strain), mean)
 101CD 101HFD  103CD 103HFD   32CD   40CD  40HFD   43CD  43HFD   44CD  44HFD
    NA     NA     NA     NA     NA     NA     NA     NA     NA     NA     NA
...
 97HFD   98CD  98HFD   99CD  99HFD
    NA     NA     NA     NA     NA
There were 50 or more warnings (use warnings() to see the first 50)

和

> ave <- daply(data, data$Strain, mean)
Error in parse(text = x) : <text>:1:4: unexpected symbol
1: 101CD

我觉得应该有一个相当简单的方法来实现这一点，但我一直无法找到解决方案。

Answer 1

您可以使用dplyr。在这里，我们对group_by进行过滤，然后使用summarise_each对每列进行汇总，并将函数mean的na.rm设置为TRUE

library(dplyr)

data %>% group_by(Strain) %>%
         summarise_each(funs(mean(., na.rm=TRUE)))

Source: local data frame [4 x 6]

  Strain   Age      X103         X3      X163       X39
  (fctr) (dbl)     (dbl)      (dbl)     (dbl)     (dbl)
1  101CD    28 -5.022326 -0.3612988 -7.616547 -3.424497
2 101HFD    30 -9.990774 -3.1286649 -3.851476 -1.135496
3  103CD    29 -5.293156 -1.9965538 -3.076994 -1.149094
4 103HFD    29 -8.583833 -1.1674327 -4.417345 -1.210476

Answer 2

利用data.frame是一种特殊的列表这一事实。

aggregate(data, data[, "Age", drop = FALSE], mean)

为了使选择结果保持为data.frame，需要使用drop = FALSE。data[, "Age"]等同于data[, "Age", drop = TRUE]，它将返回一个向量。