R/explore.R

In matloff/rectools: Advanced Recommender System

# generates a sequence of plots exploring input data
# to add: rating vs covariate
# arguments:


#   ratingsIn: input data, with first cols (userID,itemID,rating,
#              covariates)
#   plotcovs: if True, generate plots for covariates (if there are any)

explore <- function(ratingsIn, plotcovs=TRUE) {
  users <- ratingsIn[,1]
  items <- ratingsIn[,2]
  ratings <- ratingsIn[,3]
  Yi. <- tapply(ratings,users,mean) # means of all ratings per user
  Y.j <- tapply(ratings,items,mean) # means of all ratings per item
  Ni. <- tapply(ratings,users,length) # number of ratings per user
  N.j <- tapply(ratings,users,length) # number of ratings per item
  
  # histograms
  hist(ratings)
  par(ask=TRUE)
  hist(Yi.)
  hist(Y.j)
  hist(Ni.)
  hist(N.j)
  
  # scatterplots
  userMeans <- sapply(users, function(x) Yi.[x])
  itemMeans <- sapply(items, function(x) Y.j[x])
  
  # plot(userMeans, ratings, main="Yi. vs Yij", xlab="Yi.", ylab="Yij")
  # plot(itemMeans, ratings, main="Y.j vs Yij", xlab="Y.j", ylab="Yij")
  
  # heatmap
  palette <- colorRampPalette(c('blue','red'))
  ratColors <- palette(10)[as.numeric(cut(ratings, breaks=10))]
  plot(userMeans, itemMeans, col=ratColors, main="Ratings Heatmap", xlab="Yi.", ylab="Y.j")
  
  # covariate plots
  if (plotcovs && ncol(ratingsIn) > 3) {
    for (i in 4:ncol(ratingsIn)) {  # plot a histogram/barchart for each covariate column
      covName = colnames(ratingsIn)[i]

      if (is.numeric(ratingsIn[,i])) {
        hist(ratingsIn[,i], main=paste("Histogram of",covName), xlab=colnames(ratingsIn)[i])
        plot(ratingsIn[,i], ratingsIn[,3], main=paste("Ratings vs ", covName), xlab="Covariate Values", ylab="Rating")
      }
      else {
        barplot(table(ratingsIn[,i]), main=paste("Bar plot of", covName), xlab=colnames(ratingsIn)[i])
        
        uniqueVals <- unique(ratingsIn[,i])
        covMeans <- sapply(uniqueVals, function(x) mean(ratingsIn[ which(ratingsIn[,i]==x), 3]))
        barplot(covMeans, main=paste("Average ratings for ", covName), xlab=colnames(ratingsIn)[i])
        # plot(uniqueVals, covMeans, main=paste("Average rating vs ", covName), xlab="Covariate Values", ylab="Average Rating")
      }
    }
  }
}