R 对满足所有可能标准的标准的所有值求和

我有一个data.table，如下所示：

a <- data.table(color=c("Red","Blue","Red","Green","Red","Blue","Blue"), count=c(1,2,6,4,2,1,1),include=c(1,1,1,1,0,0,1))

> a
     color count include
[1,]   Red     1       1
[2,]  Blue     2       1
[3,]   Red     6       1
[4,] Green     4       1
[5,]   Red     2       0
[6,]  Blue     1       0
[7,]  Blue     1       1

> a[,include == 1,list(quantity=sum(count))]
Error in `[.data.table`(a, , include == 1, list(quantity = sum(count))) : 
  Each item in the 'by' or 'keyby' list must be same length as rows in x (7): 1

我尝试了以下方法，在过去取得了一些成功：

> a[,include == 1,list(total=sum(count)),by=colour]
Error in `[.data.table`(a, , include == 1, list(quantity = sum(count)),  : 
  Provide either 'by' or 'keyby' but not both

当

a

没有钥匙，且钥匙颜色为

时，会收到相同的错误消息。我还尝试了以下操作，将按键设置为
color
：

a <- data.table(color=c("Red","Blue","Red","Green","Red","Blue","Blue"), count=c(1,2,6,4,2,1,1),include=c(1,1,1,1,0,0,1))

> a
     color count include
[1,]   Red     1       1
[2,]  Blue     2       1
[3,]   Red     6       1
[4,] Green     4       1
[5,]   Red     2       0
[6,]  Blue     1       0
[7,]  Blue     1       1

> a[,include == 1,list(quantity=sum(count))]
Error in `[.data.table`(a, , include == 1, list(quantity = sum(count))) : 
  Each item in the 'by' or 'keyby' list must be same length as rows in x (7): 1

我找不到其他好的解决办法。非常感谢您的帮助。
这应该行得通

library(data.table)
a <- data.table(color=c("Red","Blue","Red","Green","Red","Blue","Blue"), count=c(1,2,6,4,2,1,1),include=c(1,1,1,1,0,0,1))
a[include == 1, list(total=sum(count)), keyby = color]

   color total
1:  Blue     3
2: Green     4
3:   Red     7

或者如果
包括
包括其他值，则：

a[, list(total=sum(count*(include==1))), keyby = color]

其中，
NA
s可能需要考虑

通过避免向量扫描
i
，这些方法可能更有效，但这在很大程度上取决于数据大小和属性。这些只需要与最大组一样大的工作记忆，而
i
中的
include==1
需要至少分配一个向量，只要
nrow（a）
@Ina，那么你只需要一个字符：第一个逗号！啊，你在开玩笑！谢谢你的帮助：）