任务1

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="rdb",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) 

  chunk$abstract<-iconv(chunk$abstract,"WINDOWS-1252","UTF-8") 

  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)

 word freq

1 signaling   15

2    across   15

3  cellular    5

4 membranes    5

5       the  160

6       826    5

任务2

install.packages("wordcloud2")

library(wordcloud2)

wordcloud2(words[0:1000,])

任务3

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')

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

wordcloud2(words2)