求和第二个df的子集

Question

我有这两个表，需要计算totalMilk作为df1 $ date1和df1 $ date2之间dod2的prod之和，其中eartag = eartag。有人请给我一个提示吗？谢谢你提前。何

library(lubridate)

df1 <- data.frame(eartag = 1:10,
                  date1 = dmy("10/10/16"),
                  date2 = dmy("10/03/17"),
                  totalMilk=NA)

df2 <- data.frame(eartag = rep(1:10,each = 10),
                  edate = rep(dmy("10/10/16") + days(1:10), times = 10),
                  prod = round(runif(100,0.5,3),1))