R help - Apr 2016 - multiplication by groups

df1 <- data.frame(ID = c(1,1,2,2,3,3,4,4,5,5),
                   A = c(1,0,5,1,1,NA,0,3,2,7),
                   B = c(2,3,NA,3,4,NA,1,0,5,NA))

df2 <- data.frame(ID = c(1,2,3,4,5),
                   A = c(1,6,1,3,9),
                   B = c(5,3,4,1,5))

m <- match(df1$ID, df2$ID)

sel <- c("A", "B")

for (i in 1:nrow(df1)) {
  df1[i,sel] <- round(df1[i,sel]/df2[m[i],sel], 2)
}
> df1
   ID    A   B
1   1 1.00 0.4
2   1 0.00 0.6
3   2 0.83  NA
4   2 0.17 1.0
5   3 1.00 1.0
6   3   NA  NA
7   4 0.00 1.0
8   4 1.00 0.0
9   5 0.22 1.0
10  5 0.78  NA
>
--

Best,

GG




	[[alternative HTML version deleted]]