在以下数据集中，我想将Size列中的值乘以Month1，Month2或Month3列中的值，具体取决于我们在Month列中的位数。因此，如果在特定行中Month的值为2，我想将Size列中的值乘以Month2列中的值，然后将结果保存在新列NewSize中。非常感谢您的提前帮助!
Orig = c("A","B","A","A","B","A","A","B","A")
Dest = c("B","A","C","B","A","C","B","A","C")
Month = c(1,1,1,2,2,2,3,3,3)
Size = c(30,20,10,10,20,20,30,50,20)
Month1 = c(1,0.2,0,1,0.2,0,1,0.2,0)
Month2 = c(0.6,1,0,0.6,1,0,0.6,1,0)
Month3 = c(0,1,0.6,0,1,0.6,0,1,0.6)
df <- data.frame(Orig,Dest,Month,Size,Month1,Month2,Month3)
df
Orig Dest Month Size Month1 Month2 Month3
1 A B 1 30 1.0 0.6 0.0
2 B A 1 20 0.2 1.0 1.0
3 A C 1 10 0.0 0.0 0.6
4 A B 2 10 1.0 0.6 0.0
5 B A 2 20 0.2 1.0 1.0
6 A C 2 20 0.0 0.0 0.6
7 A B 3 30 1.0 0.6 0.0
8 B A 3 50 0.2 1.0 1.0
9 A C 3 20 0.0 0.0 0.6
最佳答案
这是一种使用ifelse的替代方法
> transform(df, NewSize=ifelse(Month==1, Size*Month1,
ifelse(Month==2, Size*Month2, Size*Month3)))
Orig Dest Month Size Month1 Month2 Month3 NewSize
1 A B 1 30 1.0 0.6 0.0 30
2 B A 1 20 0.2 1.0 1.0 4
3 A C 1 10 0.0 0.0 0.6 0
4 A B 2 10 1.0 0.6 0.0 6
5 B A 2 20 0.2 1.0 1.0 20
6 A C 2 20 0.0 0.0 0.6 0
7 A B 3 30 1.0 0.6 0.0 0
8 B A 3 50 0.2 1.0 1.0 50
9 A C 3 20 0.0 0.0 0.6 12