任务一：

library(RMySQL)

killDbConnections <- function () {

  all_cons <- dbListConnections(MySQL())

  print(all_cons)

  for(con in all_cons)

    +  dbDisconnect(con)

  print(paste(length(all_cons), " connections killed."))

}

killDbConnections()

con <- dbConnect(MySQL(),host="localhost",dbname="rdb2",user="root",password="")

dbSendQuery(con,'SET NAMES utf8')

rs <- dbSendQuery(con, "SELECT * FROM article WHERE isdone=1")

words = data.frame(word=c(), freq = c())

while (!dbHasCompleted(rs)) {

+     chunk<-dbFetch(rs,10)

+     count<-nrow(chunk)

+     cnt=1

+     while (cnt<=count) {

+         str=gsub("[[:punct:]]", "", tolower(chunk[cnt,5]))

+         temp=as.vector(unlist(strsplit(str, split = " ")))

+         temp_len=length(temp)

+         cnt2=1

+         while (cnt2 <= temp_len) {

+             if(temp[cnt2] %in% words$word){words[words$word == temp[cnt2],]$freq = words[words$word == temp[cnt2],]$freq+1}

+             else{words = rbind(words,data.frame(word=c(temp[cnt2]),freq=c(1)))}

+             cnt2=cnt2+1

+         }

+         cnt=cnt+1

+     }

+ }

head(words)

任务二：

library(wordcloud2)

wordcloud2(words[0:1000,])

任务三：

new_words = words[order(words$freq,decreasing=T),]

del_word = c('of','the','and','in','to','a','that','is','for','buy','with','we','are','an','this','these','as','from','which','at','their','have','or','our','its','but','how','be','as','here','on','can','into','data','between','both','also','by')

words2 = words[which(!(words$word %in% del_word)),]

words2 = words2[order(words2$freq,decreasing=T),]

wordcloud2(words2)