我可以通過變異從一個組創建多個列嗎？

Question

我想將某個列上的數據組分組，然後將函數應用於返回多個列的分組數據。藉助於舉例，考慮以下

Names = append(rep('Mark',10),rep('Joe',10)) 
Spend = rnorm(length(Names),50,0.5) 

df <- data.frame(
    Names, 
    Spend 
) 


get.mm <- function(data){ 


    return(list(median(data),mean(data))) 
} 

這裏，get.mm返回兩個數字的列表。我想申請get.mm到df %>% group_by(Names)並且結果有兩列，每個輸出一個函數。

期望的結果應該是

Names median mean 
    <fctr> <dbl> <dbl> 
1 Joe 49.89284 49.9504 
2 Mark 50.17244 50.0735 

我在這裏簡單的功能演示的方式，我知道我可能只是不喜歡

df %>% group_by(Names) %>% summarise(median = median(Spend), mean = mean(Spend)) 

Answer 1

東西，如果你重寫get.mm使其返回數據幀，則可以使用group_by %>% do：

get.mm <- function(data){ 
    data.frame(median = median(data), mean = mean(data)) 
} 

df %>% group_by(Names) %>% do(get.mm(.$Spend)) 
# here . stands for a sub data frame with a unique Name, .$Spend passes the corresponding 
# column to the function 

---

重複的例子：

set.seed(1) 
Names = append(rep('Mark',10),rep('Joe',10)) 
Spend = rnorm(length(Names),50,0.5) 
df <- data.frame(Names, Spend) 

df %>% group_by(Names) %>% do(get.mm(.$Spend)) 

# A tibble: 2 x 3 
# Groups: Names [2] 
# Names median  mean 
# <fctr> <dbl> <dbl> 
#1 Joe 50.24594 50.12442 
#2 Mark 50.12829 50.06610 

df %>% group_by(Names) %>% summarise(median = median(Spend), mean = mean(Spend)) 

# A tibble: 2 x 3 
# Names median  mean 
# <fctr> <dbl> <dbl> 
#1 Joe 50.24594 50.12442 
#2 Mark 50.12829 50.06610