Create test and validation sets

Create edx set, validation set, and submission file

if(!require(tidyverse)) install.packages(“tidyverse”, repos = “http://cran.us.r-project.org”)
if(!require(caret)) install.packages(“caret”, repos = “http://cran.us.r-project.org”)

MovieLens 10M dataset:

https://grouplens.org/datasets/movielens/10m/

http://files.grouplens.org/datasets/movielens/ml-10m.zip

dl <- tempfile() download.file(“http://files.grouplens.org/datasets/movielens/ml-10m.zip”, dl) ratings <- read.table(text = gsub(“::”, “\t”, readLines(unzip(dl, “ml-10M100K/ratings.dat”))), col.names = c(“userId”, “movieId”, “rating”, “timestamp”)) movies <- str_split_fixed(readLines(unzip(dl, “ml-10M100K/movies.dat”)), “\\::”, 3) colnames(movies) <- c(“movieId”, “title”, “genres”) movies <- as.data.frame(movies) %>% mutate(movieId = as.numeric(levels(movieId))[movieId],
title = as.character(title),
genres = as.character(genres))
movielens <- left_join(ratings, movies, by = “movieId”)

Validation set will be 10% of MovieLens data

set.seed(1)
test_index <- createDataPartition(y = movielens$rating, times = 1, p = 0.1, list = FALSE)
edx <- movielens[-test_index,]
temp <- movielens[test_index,]

Make sure userId and movieId in validation set are also in edx set

validation <- temp %>%
semi_join(edx, by = “movieId”) %>%
semi_join(edx, by = “userId”)

Add rows removed from validation set back into edx set

removed <- anti_join(temp, validation)
edx <- rbind(edx, removed)
rm(dl, ratings, movies, test_index, temp, movielens, removed)