在R中使用`apply`的变体 [英] Using variations of `apply` in R

问题描述

通常在研究中，我们必须做一个汇总表.我想在R中使用tapply创建一个表.唯一的问题是我有40个变量，并且我希望基本上对所有40个变量执行相同的操作.这是数据示例

Often times in research we have to do a summary table. I would like to create a table using tapply in R. The only problem is I have 40 variables and I would like to basically perform the same operation for all 40 variables. Here is an example of the data

Age Wt  Ht  Type
79  134 66  C
67  199 64  C
39  135 78  T
92  149 61  C
33  138 75  T
68  139 71  C
95  198 62  T
65  132 65  T
56  138 81  C
71  193 78  T

基本上，我想让它产生给定 Type 的所有变量的均值.看起来应该是

Essentially I would like to get it to produce the means of all the variables given the Type. It should look as

      C     T
Age 72.4   60.6
Wt  151.8  159.2
Ht  68.6   71.6

我尝试使用

sapply(df, tapply(df, df$Type, mean)) 

但出现错误.

任何指导将不胜感激.

Any guidance would be appreciated.

推荐答案

尝试:

> sapply(df[1:3], tapply, df$Type, mean)
   Age    Wt   Ht
C 72.4 151.8 68.6
T 60.6 159.2 71.6

或者您可以使用colMeans:

> sapply(split(df[1:3], df$Type), colMeans)
        C     T
Age  72.4  60.6
Wt  151.8 159.2
Ht   68.6  71.6

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