轻按或汇总语句中的多个功能 [英] Multiple functions in a single tapply or aggregate statement

问题描述

是否可以在一个tapply或聚合语句中包含两个函数？

Is it possible to include two functions within a single tapply or aggregate statement?

下面我使用两个tapply语句和两个聚合语句：一个用于均值，一个用于SD。

我希望合并这些语句。

Below I use two tapply statements and two aggregate statements: one for mean and one for SD.
I would prefer to combine the statements.

my.Data = read.table(text = "
  animal    age     sex  weight
       1  adult  female     100
       2  young    male      75
       3  adult    male      90
       4  adult  female      95
       5  young  female      80
", sep = "", header = TRUE)

with(my.Data, tapply(weight, list(age, sex), function(x) {mean(x)}))
with(my.Data, tapply(weight, list(age, sex), function(x) {sd(x)  }))

with(my.Data, aggregate(weight ~ age + sex, FUN = mean)
with(my.Data, aggregate(weight ~ age + sex, FUN =   sd)

# this does not work:

with(my.Data, tapply(weight, list(age, sex), function(x) {mean(x) ; sd(x)}))

# I would also prefer that the output be formatted something similar to that 
# show below.  `aggregate` formats the output perfectly.  I just cannot figure 
# out how to implement two functions in one statement.

  age    sex   mean        sd
adult female   97.5  3.535534
adult   male     90        NA
young female   80.0        NA
young   male     75        NA

我总是可以运行两个单独的语句并合并输出。我只是希望可能会有
a稍微方便一些的解决方案。

I can always run two separate statements and merge the output. I was just hoping there might be a slightly more convenient solution.

我在这里找到了下面的答案：使用tapply将多个函数应用于列

I found the answer below posted here: Apply multiple functions to column using tapply

f <- function(x) c(mean(x), sd(x))
do.call( rbind, with(my.Data, tapply(weight, list(age, sex), f)) )

但是，行或列均未标记。

However, neither the rows or columns are labeled.

     [,1]     [,2]
[1,] 97.5 3.535534
[2,] 80.0       NA
[3,] 90.0       NA
[4,] 75.0       NA

我更喜欢基数R中的解决方案。 plyr 软件包中的解决方案发布在上面的链接中。如果我可以在上述输出中添加正确的行和列标题，那将是完美的。

I would prefer a solution in base R. A solution from the plyr package was posted at the link above. If I can add the correct row and column headings to the above output, it would be perfect.

推荐答案

但是这些应该具有：

with(my.Data, aggregate(weight, list(age, sex), function(x) { c(MEAN=mean(x), SD=sd(x) )}))

with(my.Data, tapply(weight, list(age, sex), function(x) { c(mean(x) , sd(x) )} ))
# Not a nice structure but the results are in there

with(my.Data, aggregate(weight ~ age + sex, FUN =  function(x) c( SD = sd(x), MN= mean(x) ) ) )
    age    sex weight.SD weight.MN
1 adult female  3.535534 97.500000
2 young female        NA 80.000000
3 adult   male        NA 90.000000
4 young   male        NA 75.

要遵循的原则是让函数返回一件事，这可以是向量或列表，但不能连续调用两个函数。

The principle to be adhered to is to have your function return "one thing" which could be either a vector or a list but cannot be the successive invocation of two function calls.

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