How I can perform NER for custom named entity. e.g. If I want to identify if particular word is skill in resume. If (Java, c++) is occurring in my text i should be able to label them as skill. I don't want to use spacy with custom corpus.I want to create the dataset e.g.
words will be my features and label(skill) will be my dependent variable.
what is the best approach to handle these kinda problems.
The alternative to custom dictionaries and gazettes is to create a dataset where you assign to each word the corrisponding label. You can define a set of labels (e.g. {OTHER, SKILL}) and create a dataset with examples like:
I OTHER
can OTHER
program OTHER
in OTHER
Python SKILL
. OTHER
And with a large enough dataset you train a model to predict the corresponding label.
You can try to get a list of "coding language" synonims (or the specific skills you are looking for) from word embeddings trained on your CV corpus and use this information to automatically label other corpora. I would say that key point is to find a way to at least partially automatize the labeling otherwise you won't have enough examples to train the model on your custom NER task. Use tools like https://prodi.gy/ that reduce the labeling effort.
As features you can also use word embeddings (or other typical NLP features like n-grams, POS tag, etc. depending on the model you are using)
Another option is to apply transfer learning from other NER/NLP models and finetune them on your CV labeled dataset.
I would put more effort in creating the right dataset and then test gradually more complex models selecting what best fit your needs.
Related
I want to fine tune BERT on a specific domain. I have texts of that domain in text files. How can I use these to fine tune BERT?
I am looking here currently.
My main objective is to get sentence embeddings using BERT.
The important distinction to make here is whether you want to fine-tune your model, or whether you want to expose it to additional pretraining.
The former is simply a way to train BERT to adapt to a specific supervised task, for which you generally need in the order of 1000 or more samples including labels.
Pretraining, on the other hand, is basically trying to help BERT better "understand" data from a certain domain, by basically continuing its unsupervised training objective ([MASK]ing specific words and trying to predict what word should be there), for which you do not need labeled data.
If your ultimate objective is sentence embeddings, however, I would strongly suggest you to have a look at Sentence Transformers, which is based on a slightly outdated version of Huggingface's transformers library, but primarily tries to generate high-quality embeddings. Note that there are ways to train with surrogate losses, where you try to emulate some form ofloss that is relevant for embeddings.
Edit: The author of Sentence-Transformers recently joined Huggingface, so I expect support to greatly improve over the upcoming months!
#dennlinger gave an exhaustive answer. Additional pretraining is also referred as "post-training", "domain adaptation" and "language modeling fine-tuning". here you will find an example how to do it.
But, since you want to have good sentence embeddings, you better use Sentence Transformers. Moreover, they provide fine-tuned models, which already capable of understanding semantic similarity between sentences. "Continue Training on Other Data" section is what you want to further fine-tune the model on your domain. You do have to prepare training dataset, according to one of available loss functions. E.g. ContrastLoss requires a pair of texts and a label, whether this pair is similar.
I believe transfer learning is useful to train the model on a specific domain. First you load the pretrained base model and freeze its weights, then you add another layer on top of the base model and train that layer based on your own training data. However, the data would need to be labelled.
Tensorflow has some useful guide on transfer learning.
You are talking about pre-training. Fine-tuning on unlabeled data is called pre-training and for getting started, you can take a look over here.
I aim to have a train set of texts written by a specific author and a larger test set of unknown texts. I want to be able to predict whether or not each text (or class) in the test set was written by the specific author of the train set of texts. What classification model should I use to achieve this and how might I implement it?
You could use a logistic regression model. Even it has "regression" in the name, it is applied to classification.
If the use of certain words is typical for your author, you could create a model that is based on frequency of words in the texts:
Before you apply the model, you need to create numerical values out of the texts. Therefore you can assign tokens to the unique words.
You create a feature vector by counting the frequency of the words
Logistic regession model for text classification contains code where these steps are executed in order to derive the judgement of a movie review.
If for example the sequence of words needs to be considered, you need a modified approach.
i been trying to learn a bit of machine learning for a project that I'm working in. At the moment I managed to classify text using SVM with sklearn and spacy having some good results, but i want to not only classify the text with svm, I also want it to be classified based on a list of keywords that I have. For example: If the sentence has the word fast or seconds I would like it to be classified as performance.
I'm really new to machine learning and I would really appreciate any advice.
I assume that you are already taking a portion of your data, classifying it manually and then using the result as your training data for the SVM algorithm.
If yes, then you could just append your list of keywords (features) and desired classifications (labels) to your training data. If you are not doing it already, I'd recommend using the SnowballStemmer on your training data features.
I am building an NLP pipeline and I am trying to get my head around in regards to the optimal structure. My understanding at the moment is the following:
Step1 - Text Pre-processing [a. Lowercasing, b. Stopwords removal, c. stemming, d. lemmatisation,]
Step 2 - Feature extraction
Step 3 - Classification - using the different types of classifier(linearSvC etc)
From what I read online there are several approaches in regard to feature extraction but there isn't a solid example/answer.
a. Is there a solid strategy for feature extraction ?
I read online that you can do [a. Vectorising usin ScikitLearn b. TF-IDF]
but also I read that you can use Part of Speech or word2Vec or other embedding and Name entity recognition.
b. What is the optimal process/structure of using these?
c. On the text pre-processing I am ding the processing on a text column on a df and the last modified version of it is what I use as an input in my classifier. If you do feature extraction do you do that in the same column or you create a new one and you only send to the classifier the features from that column?
Thanks so much in advance
The preprocessing pipeline depends mainly upon your problem which you are trying to solve. The use of TF-IDF, word embeddings etc. have their own restrictions and advantages.
You need to understand the problem and also the data associated with it. In order to make the best use of the data, we need to implement the proper pipeline.
Specifically for text related problems, you will find word embeddings to be very useful. TF-IDF is useful when the problem needs to be solved emphasising the words with lesser frequency. Word embeddings, on the other hand, convert the text to a N-dimensional vector which may show up similarity with some other vector. This could bring a sense of association in your data and the model can learn the best features possible.
In simple cases, we can use a bag of words representation to tokenize the texts.
So, you need to discover the best approach for your problem. If you are solving a problems which closely resembles the famous NLP problems like IMDB review classification, sentiment analysis on Twitter data, then you can find a number of approaches on the internet.
I am trying to build a classifier to detect subjectivity. I have text files tagged with subjective and objective . I am little lost with the concept of features creation from this data. I have found the lexicon of the subjective and objective tag. One thing that I can do is to create a feature of having words present in respective dictionary. Maybe the count of words present in subjective and objective dictionary. After that I intend to use naive bayes or SVM to develop the model
My problem is as follow
Is my approach correct ?
Can I create more features ? If possible suggest some or point me to some paper or link
Can I do some test like chi -sq etc to identify effective words from the dictionary ?
You are basically on the right track. I would try and apply classifier with features you already have and see how well it will work, before doing anything else.
Actually best way to improve your work is to google for subjectivity classification papers and read them (there are a quite a number of them). For example this one lists typical features for this task.
And yes Chi-squared can be used to construct dictionaries for text classification (other commonly used methods are TD*IDF, pointwise mutal information and LDA)
Also, recently new neural network-based methods for text classification such as paragraph vector and dynamic convolutional neural networks with k-max pooling demonstrated state-of-the-art results on sentiment analysis, thus they should probably be good for subjectivity classification as well.