長data變窄data

注重基礎函數的應用，用了兩個比較常用的package

library(plyr)
library(rlist)
A <- data.frame(a = c(rep("A",3),
                      rep("B",3),
                      rep("C",4)),
                b = c(1,2,3,4,5,6,7,8,9,0))
da  <- dlply(A, .(a),c)
da1 <- list.flatten(da)
da2 <- da1[laply(da1, is.numeric)]
re <- NULL
for(i in 1:length(da2))
{
  re <- c(re,paste(da2[[i]],sep = "", 
                   collapse = ""))
}
data.frame(name = unique(A$a), result = re)