R语言实战实现基于用户的简单的推荐系统（数量较少）

a<-c(1,1,1,1,2,2,2,2,3,3,3,4,4,4,5,5,5,5,6,6,7,7)

b<-c(1,2,3,4,2,3,4,5,4,1,2,3,2,4,5,2,6,4,1,2,3,4)

da<-data.frame(a,b)

a<-c(1,1,2,2,3,3,3,3,3,4,4,5,5,5,6,6,7,7)

b<-c(2,5,7,2,6,4,7,1,8,6,3,3,4,1,2,4,4,9)

da2<-data.frame(a,b)

ax<-unique(da$a)

bx<-unique(da$b)

m<-matrix(0,max(ax),max(ax))

for(i in 1:max(ax))

{

  for(j in 1:max(ax))

  {

    if(i==j)

    {

      m[i,j]=0

    }else{

       m[i,j]=length(intersect(t(da[which(da$a==i),][2]),t(da[which(da$a==j),][2])))

    }

  }

}

m

myfun<-function(da,k,da2,m)

{

  uid<-unique(c)

  pre=0

  recall=0

  for (mm in 1:max(uid))

  {

    aa<-which(rank(-m[mm,])<k)

    bb<-unique(da[unlist(lapply(da$a,function(x){

    length(intersect(x,aa))!=0

    })),][2])

    movie<-setdiff(t(bb),t((da[which(da$a==mm),][2])))

    movie2<-t(da2[da2$a==mm,][2])

    p<-length(intersect(movie,movie2))/length(movie)

    r<-length(intersect(movie,movie2))/length(movie2)

    pre<-pre+p

    recall<-recall+r

    if(mm==1)

    {

      user_top1<-which(rank(-m[mm,])<k)

      movie_top2<-sort(movie[rank(movie)<k])

      print(user_top1)

      print(movie_top2)

    }

  }

  preA<-pre/length(uid);

  recallA<-recall/length(uid);

  dataframe<-data.frame(c(k),preA,recallA)

  return(dataframe)

}

df<-myfun(da,4,da2,m);

preA<-c()

recallA<-c()

k<-c()

daa<-data.frame(k,preA,recallA)

for(i in 3:7)

{

  df<-myfun(da,i,da2,m);

  daa<-rbind(daa,df)

}

daa

library(ggplot2)

qplot(preA,recallA,data=daa ,geom = c("point", "smooth"))

preA<-c()recallA<-c()k<-c()daa<-data.frame(k,preA,recallA)