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Netflix Prize(百万美元大奖)数据预处理的一个简单R程序

不知道这样一个程序要跑多久:

files = list.files("training_set", full.names = T)
writeLines("movieID,customerID,Rating,ratingDate,movieReleaseDate",
   "training_set.csv")
for (i in 1:17770) {
   x = read.csv(files[i], F, skip = 1, as.is = F, stringsAsFactors = F)
   x = cbind(i, x, read.csv("movie_titles.txt", F, nrows = 1,
       skip = i - 1, as.is = F, stringsAsFactors = F)[1, 2])
   write.table(x, file = "training_set.csv", append = T, sep = ",",
       row.names = F, col.names = F, quote = F)
}

当我没加入第7~8行的read.csv()那一句时,程序在WinXP+奔四3.0GHz+512M内存下跑了47分钟把一个2G多的CSV数据文件写完了。不过等我用SQL语句去读其中一列时,发现内存终于不够用了。

Netflix的奖金是$1,000,000,呃,这么大一堆钱,做做梦吧。莫非这个奖还要比拼各家的计算机配置?国内啥时候能有这样的悬赏啊?