使用data.frame对满足条件的所有值求和

Question

我正在尝试使用数据框执行与this类似的操作。

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更新：2013/06/14

scores <- data.frame( Type=c("Disc","HW","Disc"), Module=c(1,1,2), Score=c(14,6,14))
weights <- data.frame ( Type=c("Disc","HW"), Weight=c(0.2,0.4))

我想应用加权因子并对得分数据框求和，以生成一个具有每个模块加权和的表。结果应如下所示：

   Module   Weighted Sum
1:      1            5.2
2:      2            2.8

有人可以帮忙吗？

Answer 1

复制该示例：

a <- data.frame(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))

  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

total = sapply(levels(a$color),function(x){sum(a$count[a$color==x & a$include==1])},USE.NAMES=F)

data.frame(color=levels(a$color),total)

  color total
1  Blue     3
2 Green     4
3   Red     7