inst/CaseStudies/MovieLens/movielens.R

In matloff/revisit: "Statistical Audit": Verify and Revisit Statistical Analysis

# analysis of MovieLens data, 
# https://grouplens.org/datasets/movielens/100k/

datapath <- system.file("data", package="revisit")
filepath <- paste0(datapath, "/u.data")
if (!file.exists(filepath)){
   download.file("http://files.grouplens.org/datasets/movielens/ml-100k/u.data", "u.data")
   file.rename("u.data", filepath)
}
# read ratings data (userID, movieID, rating, timestamp)
ud <- read.table(filepath,header=F,sep='\t')

filepath <- paste0(datapath, "/u.user")
if (!file.exists(filepath)){
   download.file("http://files.grouplens.org/datasets/movielens/ml-100k/u.user", "u.user")
   file.rename("u.user", filepath)
}
# read user covariate data (user, age, gender, ...(
uu <- read.table(filepath,header=F,sep='|')

ud <- ud[,-4]   # remove timestamp, leaving user, item, rating
uu <- uu[,1:3]  
names(ud) <- c('user','item','rating')
names(uu) <- c('user','age','gender')
uu$gender <- as.integer(uu$gender == 'M')
uall <- merge(ud,uu)

# investigate effect of age, gender on user mean ratings
usermeans <- tapply(uall$rating,uall$user,mean)
lmout <- lm(usermeans ~ uu[,2] + uu[,3])
print(summary(lmout))  # get estimates, p-values etc.