All:
I am beginner in R topic modeling, it all started three weeks ago. So my problem is I can successfully processed my data into corpus, Document term matrix and LDA function. I have tweets as my input and about 460,000 tweets. But I am not happy with the result, the words across all topic are very similar.
packages <- c('tm','topicmodels','SnowballC','RWeka','rJava')
if (length(setdiff(packages, rownames(installed.packages()))) > 0) {
install.packages(setdiff(packages, rownames(installed.packages())))
}
options( java.parameters = "-Xmx4g" )
library(tm)
library(topicmodels)
library(SnowballC)
library(RWeka)
print("Please select the input file");
flush.console();
ifilename <- file.choose();
raw_data=scan(ifilename,'string',sep="\n",skip=1);
tweet_data=raw_data;
rm(raw_data);
tweet_data = gsub("(RT|via)((?:\\b\\W*@\\w+)+)","",tweet_data)
tweet_data = gsub("http[^[:blank:]]+", "", tweet_data)
tweet_data = gsub("@\\w+", "", tweet_data)
tweet_data = gsub("[ \t]{2,}", "", tweet_data)
tweet_data = gsub("^\\s+|\\s+$", "", tweet_data)
tweet_data = gsub('\\d+', '', tweet_data)
tweet_data = gsub("[[:punct:]]", " ", tweet_data)
max_size=5000;
data_size=length(tweet_data);
itinerary=ceiling(data_size[1]/max_size);
if (itinerary==1){pre_data=tweet_data}else {pre_data=tweet_data[1:max_size]}
corp <- Corpus(VectorSource(pre_data));
corp<-tm_map(corp,tolower);
corp<-tm_map(corp,removePunctuation);
extend_stop_word=c('description:','null','text:','description','url','text','aca',
'obama','romney','ryan','mitt','conservative','liberal');
corp<-tm_map(corp,removeNumbers);
gc();
IteratedLovinsStemmer(corp, control = NULL)
gc();
corp<-tm_map(corp,removeWords,c(stopwords('english'),extend_stop_word));
gc();
corp <- tm_map(corp, PlainTextDocument)
gc();
dtm.control = list(tolower= F,removePunctuation=F,removeNumbers= F,
stemming= F, minWordLength = 3,weighting= weightTf,stopwords=F)
dtm = DocumentTermMatrix(corp, control=dtm.control)
gc();
#dtm = removeSparseTerms(dtm,0.99)
dtm = dtm[rowSums(as.matrix(dtm))>0,]
gc();
best.model <- lapply(seq(2,50, by=2), function(k){LDA(dtm[1:10,], k)})
gc();
best.model.logLik <- as.data.frame(as.matrix(lapply(best.model, logLik)))
best.model.logLik.df <- data.frame(topics=c(seq(2,50, by=2)), LL=as.numeric(as.matrix(best.model.logLik)))
k=best.model.logLik.df[which.max(best.model.logLik.df$LL),1];
cat("Best topic number is k=",k);
flush.console();
gc();
lda.model = LDA(dtm, k,method='VEM')
gc();
write.csv(terms(lda.model,50), file = "terms.csv");
lda_topics=topics(lda.model,1);
The following is the results I get:
> terms(lda.model,10)
Topic 1 Topic 2 Topic 3 Topic 4 Topic 5
[1,] "taxes" "medicare" "tax" "tax" "jobs"
[2,] "pay" "will" "returns" "returns" "plan"
[3,] "welfare" "tax" "gop" "taxes" "gop"
[4,] "will" "care" "taxes" "will" "military"
[5,] "returns" "can" "abortion" "paul" "will"
[6,] "plan" "laden" "can" "medicare" "tax"
[7,] "economy" "vote" "tcot" "class" "paul"
[8,] "budget" "economy" "muslim" "budget" "campaign"
[9,] "president" "taxes" "campaign" "says" "says"
[10,] "reid" "just" "economy" "cuts" "can"
Topic 6 Topic 7 Topic 8 Topic 9
[1,] "medicare" "tax" "medicare" "tax"
[2,] "taxes" "medicare" "tax" "president"
[3,] "plan" "taxes" "jobs" "jobs"
[4,] "tcot" "tcot" "tcot" "taxes"
[5,] "budget" "president" "foreign" "medicare"
[6,] "returns" "jobs" "plan" "tcot"
[7,] "welfare" "budget" "will" "paul"
[8,] "can" "energy" "economy" "health"
[9,] "says" "military" "bush" "people"
[10,] "obamacare" "want" "now" "gop"
Topic 10 Topic 11 Topic 12
[1,] "tax" "gop" "gop"
[2,] "medicare" "tcot" "plan"
[3,] "tcot" "military" "tax"
[4,] "president" "jobs" "taxes"
[5,] "gop" "energy" "welfare"
[6,] "plan" "will" "tcot"
[7,] "jobs" "ohio" "military"
[8,] "will" "abortion" "campaign"
[9,] "cuts" "paul" "class"
[10,] "paul" "budget" "just"
As you can see the words "tax" "medicare" are across all topic. I noticed that while I playing with the dtm = removeSparseTerms(dtm,0.99) the results may changes a little. And the following is my sample input data
> tweet_data[1:10]
[1] " While Romney friends get richer MT Romney Ryan Economic Plans Would Increase Unemployment Deepen Recession"
[2] "Wayne Allyn Root claims proof of Obama s foreign citizenship During a radio show interview Resist"
[3] " President Obama Chief Investor Leave Energy Upgrades to the Businesses Reading President Obama誷 latest Execu "
[4] " Brotherhood starts crucifixions Opponents of Egypt s Muslim president executed naked on trees Obama s tcot"
[5] " Say you stand with President Obama裻he candidate in this election who trusts women to make their own health decisions "
[6] " Romney Ryan Descend Into Medicare Gibberish "
[7] "Maddow Romney demanded opponents tax returns and lied about residency in The Raw Story"
[8] "Is it not grand How can Jews reconcile Obama Carter s treatment of Jews Israel How ca "
[9] " The Tax Returns are Hurting Romney Badly "
[10] " Replacing Gen Dempsey is cruicial to US security Dempsey disappointed by anti Obama campaign by ex military members h "
Please Help!!Thanks!
Reduce the number of topics in your case. This would enhance the clustering capability of your topic model. Now you are overlapping existing models with another. Since topic index varies over iterations, it is difficult to follow through on the results/ compare too.
来源：https://stackoverflow.com/questions/26197458/r-lda-topic-modeling-result-topics-contains-very-similar-words