joining "one-to-many"

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