来占个地方 

#任务1
library(RMySQL)
#数据库连接删除函数，每个任务之前最好先清理所有的连接，调用此函数就可以
killDbConnections <- function () {
  all_cons <- dbListConnections(MySQL())
  print(all_cons)
  for(con in all_cons)
    +  dbDisconnect(con)
  print(paste(length(all_cons), " connections killed."))
}
killDbConnections()
#创建数据库连接  
con <- dbConnect(MySQL(),host="localhost",dbname="rdb2",user="root",password="")
dbSendQuery(con,'SET NAMES utf8')
rs <- dbSendQuery(con, "SELECT * FROM article WHERE isdone=1")
#下面开始新的代码
words = data.frame(word=c(), freq = c())
while (!dbHasCompleted(rs)) {
  chunk <- dbFetch(rs, 10)
  #chunk[,4]为title, #chunk[,5]为abstract
  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2
library(wordcloud2)
wordcloud2(words[0:1000,]) 
 
#任务3
#按照freq的降序排列
new_words = words[order(words$freq,decreasing=T),]
#去掉一些定冠词等 of and the
del_word = c('not','two','other','during','of','it','may','the','and','in','to','a','that','is','for','by','with','we','are','an','this','these','as','from','which','at','their','have','or','our','its','but','how','be','as','here','on','can','into','data','between','both','also')
words2 =words[which(!(words$word %in% del_word)),]
wordcloud2(words2)