# -*- coding: utf-8 -*-
"""
Created on Mon Oct 9 19:33:00 2017
@author: wjw
"""
import pandas as pd
import numpy as np
import os
 
def difference(left,right,on): #求兩個(gè)dataframe的差集
 df = pd.merge(left,right,how='left',on=on) #參數(shù)on指的是用于連接的列索引名稱
 left_columns = left.columns
 col_y = df.columns[-1] # 得到最后一列
 df = df[df[col_y].isnull()]#得到boolean的list
 df = df.iloc[:,0:left_columns.size]#得到的數(shù)據(jù)里面還有其他同列名的column
 df.columns = left_columns # 重新定義columns
 return df
 
def readfile(filepath): #讀取文件，同時(shí)得到訓(xùn)練集和測(cè)試集
 
 pwd = os.getcwd()#返回當(dāng)前工程的工作目錄
 os.chdir(os.path.dirname(filepath))
 #os.path.dirname()獲得filepath文件的目錄；chdir()切換到filepath目錄下
 initialData = pd.read_csv(os.path.basename(filepath))
 #basename()獲取指定目錄的相對(duì)路徑
 os.chdir(pwd)#回到先前工作目錄下
 predData = initialData.iloc[:,0:3] #將最后一列數(shù)據(jù)去掉
 newIndexData = predData.drop_duplicates()
 trainData = newIndexData.sample(axis=0,frac = 0.1) #90%的數(shù)據(jù)作為訓(xùn)練集
 testData = difference(newIndexData,trainData,['userId','movieId']).sample(axis=0,frac=0.1)
 return trainData,testData
 
def getmodel(train):
 slowRate = 0.99
 preRmse = 10000000.0
 max_iter = 100
 features = 3
 lamda = 0.2
 gama = 0.01 #隨機(jī)梯度下降中加入，防止更新過度
 user = pd.DataFrame(train.userId.drop_duplicates(),columns=['userId']).reset_index(drop=True) #把在原來(lái)dataFrame中的索引重新設(shè)置，drop=True并拋棄
 
 movie = pd.DataFrame(train.movieId.drop_duplicates(),columns=['movieId']).reset_index(drop=True)
 userNum = user.count().loc['userId'] #671
 movieNum = movie.count().loc['movieId'] 
 userFeatures = np.random.rand(userNum,features) #構(gòu)造user和movie的特征向量集合
 movieFeatures = np.random.rand(movieNum,features)
 #假設(shè)每個(gè)user和每個(gè)movie有3個(gè)feature
 userFeaturesFrame =user.join(pd.DataFrame(userFeatures,columns = ['f1','f2','f3']))
 movieFeaturesFrame =movie.join(pd.DataFrame(movieFeatures,columns= ['f1','f2','f3']))
 userFeaturesFrame = userFeaturesFrame.set_index('userId')
 movieFeaturesFrame = movieFeaturesFrame.set_index('movieId') #重新設(shè)置index
 
 for i in range(max_iter): 
  rmse = 0
  n = 0
  for index,row in user.iterrows():
   uId = row.userId
   userFeature = userFeaturesFrame.loc[uId] #得到userFeatureFrame中對(duì)應(yīng)uId的feature
 
   u_m = train[train['userId'] == uId] #找到在train中userId點(diǎn)評(píng)過的movieId的data
   for index,row in u_m.iterrows(): 
    u_mId = int(row.movieId)
    realRating = row.rating
    movieFeature = movieFeaturesFrame.loc[u_mId] 
 
    eui = realRating-np.dot(userFeature,movieFeature)
    rmse += pow(eui,2)
    n += 1
    userFeaturesFrame.loc[uId] += gama * (eui*movieFeature-lamda*userFeature) 
    movieFeaturesFrame.loc[u_mId] += gama*(eui*userFeature-lamda*movieFeature)
  nowRmse = np.sqrt(rmse*1.0/n)
  print('step:%f,rmse:%f'%((i+1),nowRmse))
  if nowRmse<preRmse:
   preRmse = nowRmse
  elif nowRmse<0.5:
   break
  elif nowRmse-preRmse<=0.001:
   break
  gama*=slowRate
 return userFeaturesFrame,movieFeaturesFrame
 
def evaluate(userFeaturesFrame,movieFeaturesFrame,test):
 test['predictRating']='NAN' # 新增一列
 
 for index,row in test.iterrows(): 
  
  print(index)
  userId = row.userId
  movieId = row.movieId
  if userId not in userFeaturesFrame.index or movieId not in movieFeaturesFrame.index:
   continue
  userFeature = userFeaturesFrame.loc[userId]
  movieFeature = movieFeaturesFrame.loc[movieId]
  test.loc[index,'predictRating'] = np.dot(userFeature,movieFeature) #不定位到不能修改值
  
 return test 
 
if __name__ == "__main__":
 filepath = r"E:\學(xué)習(xí)\研究生\推薦系統(tǒng)\ml-latest-small\ratings.csv"
 train,test = readfile(filepath)
 userFeaturesFrame,movieFeaturesFrame = getmodel(train)
 result = evaluate(userFeaturesFrame,movieFeaturesFrame,test)