R define dimensions of empty data frame

Question

I am trying to collect some data from multiple subsets of a data set and need to create a data frame to collect the results. My problem is don\'t know how to create an empt

Answer 1

You can do something like:

N <- 10
collect1 <- data.frame(id   = integer(N),
                       max1 = numeric(N),
                       min1 = numeric(N))

Now be careful that in the rest of your code, you forgot to use the row index for filling the data.frame row by row. It should be:

for(i in seq_len(N)){
   collect1$id[i] <- i
   ss1 <- subset(df1, df1$id == i)
   collect1$max1[i] <- max(ss1$value)
   collect1$min1[i] <- min(ss1$value)
}

Finally, I would say that there are many alternatives for doing what you are trying to accomplish, some would be much more efficient and use a lot less typing. You could for example look at the aggregate function, or ddply from the plyr package.