Hello list, I am wondering if a joining "one-to-many" can be done a little bit easier. I tried merge function but I was not able to do it, so I end up using for and if. Suppose you have a table with locations, each location repeated several times, and some attributes at that location. The second table has the same locations, but only once with a different set of attributes. I would like to add the second set of attributes to the first table. Example: set.seed <- 123 loc <- c(rep("L1", 3), rep("L2", 5), rep("L3", 2)) val1 <- round(rnorm(10),2) val2 <- c("a", "b", "c", "a", "b", "d", "f", "e", "b", "e") t1 <- data.frame(loc, val1, val2) t2 <- data.frame(loc=c("L1","L2","L3"), val3 = c("m", "n", "p"), val4 = c(25, 67, 48)) # join one-to-many n <- nrow(t1) m <- nrow(t2) t1$val3 <- rep(1, n) t1$val4 <- rep(1, n) for (i in 1:n) { for (j in 1:m){ if (t1$loc[i]==t2$loc[j]) { t1$val3[i] <- as.character(t2$val3[j]) t1$val4[i] <- t2$val4[j] } } } Desired result:
t1 loc val1 val2 val3 val4 1 L1 -0.41 a m 25 2 L1 -0.69 b m 25 3 L1 0.36 c m 25 4 L2 1.11 a n 67 5 L2 0.15 b n 67 6 L2 -0.80 d n 67 7 L2 -0.08 f n 67 8 L2 -1.01 e n 67 9 L3 -1.01 b p 48 10 L3 -2.50 e p 48 This code works OK but it is slow if the data frames are actually bigger than my little example. I hope somebody knows of a better way of doing these type of things. Thanks, Monica _________________________________________________________________ 22009 ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.