r data.table函数通过多个变量进行聚合

我一直在尝试推广一个函数，在这个函数中，我使用不同的键进行许多不同的聚合，然后将它们合并在一起。 首先是一个示例data.table：

DT <- data.table(
                  Key1=c("giallo","giallo","giallo","verde","verde","verde","verde","verde"),
                  Key2=c("M","M","L","S","M","M","M","L"),
                  Filtro=c(1,1,1,0,0,0,1,1),
                  Var1=c(1,4,5,3,7,5,8,1),
                  Var2=c(11,24,15,33,17,45,38,21)
               )

---

DT如何将这些键作为1个向量而不是2个向量传递

Tavola <- function(s,chiaves)
{

  Tavola1 <- s[,
               list(
                 Somma11=sum(Var1),
                 Somma12=sum(Var2),
                 Media11=mean(Var1),
                 Media12=mean(Var2)),
                 by=chiaves
               ]
  print(Tavola1)
  Tavola2 <- s[Filtro==1,
               list(
                 Somma21=sum(Var1),
                 Somma22=sum(Var2),
                 Media21=mean(Var1),
                 Media22=mean(Var2)),
                 by=chiaves
               ]
  print(Tavola2)
  Tavola3 <- s[Filtro==1 & Var1>3,
               list(
                 Somma32=sum(Var2),
                 Media32=mean(Var2)),
                 by=chiaves
               ]

  print(Tavola3)
  mymerge = function(x,y) merge(x,y,by=(chiaves),all=TRUE)
  TavolaFinale <- Reduce(mymerge,list(Tavola1,Tavola2,Tavola3))

  return(TavolaFinale)
}
TavolaStat <- Tavola(s=DT,c("Key1","Key2"))

Tavola感谢您的编辑。你不能用
c（chiave1，chiave2）
代替这个
列表
和
eval
业务吗？使用
c（）
，当一个元素为
NULL
时，它将从向量中删除。@Frank：第一个函数将chiave1和chiave2作为参数，但在函数体中仅使用chiave1。第二个函数尝试使用both@Frank，谢谢，它很管用。我一直使用by中的列表作为data.table
    Tavola <- function(s,chiave1,chiave2=NULL)
    {
    
       Tavola1 <- s[,
                    by=list(eval((chiave1)),eval(chiave2)),
                    list(
                         Somma11=sum(Var1),
                         Somma12=sum(Var2),
                         Media11=mean(Var1),
                         Media12=mean(Var2)
                        )
                    ]
       print(Tavola1)
       Tavola2 <- s[Filtro==1,
                    by=list(eval(chiave1),eval(chiave2)),
                    list(
                          Somma21=sum(Var1),
                          Somma22=sum(Var2),
                          Media21=mean(Var1),
                          Media22=mean(Var2)
                        )
                   ]
       print(Tavola2)
       Tavola3 <- s[Filtro==1 & Var1>3,
                    by=list(eval(chiave1),eval(chiave2)),
                    list(
                          Somma32=sum(Var2),
                          Media32=mean(Var2)
                        )
                   ]
    
       print(Tavola3)
       mymerge = function(x,y) merge(x,y,by=c(chiave1,chiave2),all=TRUE)
       TavolaFinale <- Reduce(mymerge,list(Tavola1,Tavola2,Tavola3))
    
       return(TavolaFinale)
    }
> TavolaStat <- Tavola(s=DT,chiave1="Key1")
 Show Traceback
 
 Rerun with Debug
 Error in `[.data.table`(s, , by = list(eval((chiave1)), eval(chiave2)),  : 
  column or expression 2 of 'by' or 'keyby' is type NULL. Do not quote column names. Usage: DT[,sum(colC),by=list(colA,month(colB))] > 
> TavolaStat <- Tavola(s=DT,chiave1="Key1",chiave2="Key2")
 Show Traceback
 
 Rerun with Debug
 Error in `[.data.table`(s, , by = list(eval((chiave1)), eval(chiave2)),  : 
  The items in the 'by' or 'keyby' list are length (1,1). Each must be same length as rows in x or number of rows returned by i (8). 

Tavola <- function(s,chiaves)
{

  Tavola1 <- s[,
               list(
                 Somma11=sum(Var1),
                 Somma12=sum(Var2),
                 Media11=mean(Var1),
                 Media12=mean(Var2)),
                 by=chiaves
               ]
  print(Tavola1)
  Tavola2 <- s[Filtro==1,
               list(
                 Somma21=sum(Var1),
                 Somma22=sum(Var2),
                 Media21=mean(Var1),
                 Media22=mean(Var2)),
                 by=chiaves
               ]
  print(Tavola2)
  Tavola3 <- s[Filtro==1 & Var1>3,
               list(
                 Somma32=sum(Var2),
                 Media32=mean(Var2)),
                 by=chiaves
               ]

  print(Tavola3)
  mymerge = function(x,y) merge(x,y,by=(chiaves),all=TRUE)
  TavolaFinale <- Reduce(mymerge,list(Tavola1,Tavola2,Tavola3))

  return(TavolaFinale)
}
TavolaStat <- Tavola(s=DT,c("Key1","Key2"))