I need your help in determining the best approach for analyzing industry-specific sentences (i.e. movie reviews) for "positive" vs "negative". I've seen libraries such as OpenNLP before, but it's too low-level - it just gives me the basic sentence composition; what I need is a higher-level structure:
- hopefully with wordlists
- hopefully trainable on my set of data
Thanks!
What you are looking for is commonly dubbed Sentiment Analysis. Typically, sentiment analysis is not able to handle delicate subtleties, like sarcasm or irony, but it fares pretty well if you throw a large set of data at it.
Sentiment analysis usually needs quite a bit of pre-processing. At least tokenization, sentence boundary detection and part-of-speech tagging. Sometimes, syntactic parsing can be important. Doing it properly is an entire branch of research in computational linguistics, and I wouldn't advise you with coming up with your own solution unless you take your time to study the field first.
OpenNLP has some tools to aid sentiment analysis, but if you want something more serious, you should look into the LingPipe toolkit. It has some built-in SA-functionality and a nice tutorial. And you can train it on your own set of data, but don't think that it is entirely trivial :-).
Googling for the term will probably also give you some resources to work with. If you have any more specific question, just ask, I'm watching the nlp-tag closely ;-)
Some approaches to sentiment analysis use strategies popular on other text classification tasks. The most common being transforming your film review into a word vector, and feeding it into a classifier algorithm as training data. Most popular data mining packages can help you here. You could have a look at this tutorial on sentiment classification illustrating how to do an experiment using the open source RapidMiner toolkit.
Incidentally, there is a good data set made available for research purposes related to detecting opinion on film reviews. It is based on IMDB user reviews, and you can check many related research work on the area and how they use the data set.
Its worth bearing in mind that the effectiveness of these methods can only be judged from a statistical viewpoint, so you can pretty much assume there will be misclassifications and cases where opinion is hard to detect. As already noticed in this thread, detecting things like irony and sarcasm can be very difficult indeed.
Related
I have a quick question and could not find the answer anywhere on the internet:
Can NLTK be used to Analyze the sentiment a certain word has within a sentence?
Like: Sentiment for iPhone: "Even though it is terrible weather outside, my iPhone makes me feel good again." = Sentiment: positive
Have you thought of breaking down the text into clauses ("it is terrible weather outside", "my iphone makes me feel good again"), and evaluating them separately? You can use the NLTK's parsers for that. This will reduce the amount of text you have to analyze, though, so it might end up doing more harm than good.
This won't help you in cases like "Microsoft Surface is no iPad, it's terrible" (where your target is "iPad"), since the sentiment is negative but the iPad wins the comparison. So perhaps you'll also want to check the syntactic analysis, and only examine sentences where your target word is the subject or object. Whether these will give you better performance is anybody's guess, I think.
I do not have much experience with NLTK but I have done some concept level sentiment analysis using NLP libraries in Java. Here is how I did it. The same approach should work for you if you are able to identify dependencies in NLTK. This approach works fine for simple rules but may not work well for complicated sentences.
Are there any tools that analyze the meaning of given sentences? Recommendations are greatly appreciated.
Thanks in advance!
I am also looking for similar tools. One thing I found recently was this sentiment analysis tool built by researchers at Stanford.
It provides a model of analyzing the sentiment of a given sentence. It's interesting and even this seemingly simple idea is quite involved to model in an accurate way. It utilizes machine learning to develop higher accuracy as well. There is a live demo where you can input sentences to analyze.
http://nlp.stanford.edu/sentiment/
I also saw this RelEx semantic dependency relationship extractor.
http://wiki.opencog.org/w/Sentence_algorithms
Some natural language understanding tools can analyze the meaning of sentences, including NLTK and Attempto Controlled English. There are several implementations of discourse representation structures and semantic parsers with a similar purpose.
There are also several parsers that can be used to generate a meaning representation from the text that is being parsed.
Situation:
I wish to perform a Deep-level Analysis of a given text, which would mean:
Ability to extract keywords and assign importance levels based on contextual usage.
Ability to draw conclusions on the mood expressed.
Ability to hint on the education level (word does this a little bit though, but something more automated)
Ability to mix-and match phrases and find out certain communication patterns
Ability to draw substantial meaning out of it, so that it can be quantified and can be processed for answering by a machine.
Question:
What kind of algorithms and techniques need to be employed for this?
Is there a software that can help me in doing this?
When you figure out how to do this please contact DARPA, the CIA, the FBI, and all other U.S. intelligence agencies. Contracts for projects like these are items of current research worth many millions in research grants. ;)
That being said you'll need to process it in layers and analyze at each of those layers. For items 2 and 3 you'll find training an SVM on n-tuples (try, 3) words will help. For 1 and 4 you'll want deeper analysis. Use a tool like NLTK, or one of the many other parsers and find the subject words in sentences and related words. Also use WordNet (from Princeton)
to find the most common senses used and take those as key words.
5 is extremely challenging, I think intelligent use of the data above can give you what you want, but you'll need to use all your grammatical knowledge and programming knowledge, and it will still be very rough grained.
It sounds like you might be open to some experimentation, in which case a toolkit approach might be best? If so, look at the NLTK Natural Language Toolkit for Python. Open source under the Apache license, and there are a couple of excellent books about it (including one from O'Reilly which is also released online under a creative commons license).
We are building a database of scientific papers and performing analysis on the abstracts. The goal is to be able to say "Interest in this topic has gone up 20% from last year". I've already tried key word analysis and haven't really liked the results. So now I am trying to move onto phrases and proximity of words to each other and realize I'm am in over my head. Can anyone point me to a better solution to this, or at very least give me a good term to google to learn more?
The language used is python but I don't think that really affects your answer. Thanks in advance for the help.
It is a big subject, but a good introduction to NLP like this can be found with the NLTK toolkit. This is intended for teaching and works with Python - ie. good for dabbling and experimenting. Also there's a very good open source book (also in paper form from O'Reilly) on the NLTK website.
This is just a guess; not sure if this approach will work. If you're looking at phrases and proximity of words, perhaps you can build up a Markov Chain? That way you can get an idea of the frequency of certain phrases/words in relation to others (based on the order of your Markov Chain).
So you build a Markov Chain and frequency distribution for the year 2009. Then you build another one at the end of 2010 and compare the frequencies (of certain phrases and words). You might have to normalize the text though.
Other than that, something that comes to mind is Natural-Language-Processing techniques (there is a lot of literature surrounding the topic!).
One simple question (but I haven't quite found an obvious answer in the NLP stuff I've been reading, which I'm very new to):
I want to classify emails with a probability along certain dimensions of mood. Is there an NLP package out there specifically dealing with this? Is there an obvious starting point in the literature I start reading at?
For example, if I got a short email something like "Hi, I'm not very impressed with your last email - you said the order amount would only be $15.95! Regards, Tom" then it might get 8/10 for Frustration and 0/10 for Happiness.
The actual list of moods isn't so important, but a short list of generally positive vs generally negative moods would be useful.
Thanks in advance!
--Trindaz on Fedang #NLP
You can do this with a number of different NLP tools, but nothing to my knowledge comes with it ready out of the box. Perhaps the easiest place to start would be with LingPipe (java), and you can use their very good sentiment analysis tutorial. You could also use NLTK if python is more your bent. There are some good blog posts over at Streamhacker that describe how you would use Naive Bayes to implement that.
Check out AlchemyAPI for sentiment analysis tools and scikit-learn or any other open machine learning library for the classifier.
if you have not decided to code the implementation, you can also have the data classified by some other tool. google prediction api may be an alternative.
Either way, you will need some labeled data and do the preprocessing. But if you use a tool that may help you get better accuracy easily.