With machine learning and data science, it’s the norm to ensure your models are trained on as much available data as possible. The general belief can be simplified with this phrase “more data, better models.” But what happens when you don’t have a large enough dataset to properly train your model? This is when data augmentation comes into play. It is a way of artificially increasing the dataset at hand by generating new data points from the existing data available, through creating copies of the dataset and making minor changes to these copied data points.
For those heavily involved in the machine learning space, data augmentation is a huge game-changer. Let’s get deeper into this fascinating technique of data augmentation and learn all about its significance in the industries of machine learning and data science.
Table of contents
- What is data augmentation?
- Why is data augmentation important?
- Implementing data augmentation
- Common data augmentation techniques
- Advanced techniques for data augmentation
- Benefits of data augmentation
- Challenges of data augmentation
- Use cases and examples
- Best practices
- Tools
- Conclusion
What is data augmentation?
As mentioned above, data augmentation is a way of increasing the size of a training dataset, artificially, by creating augmented versions of the already existing data points. But how is this done? It’s a process involving various modifications to the original data, such as rotations, translations, scaling, cropping, and flipping, to create completely new and diverse data points that are still close to the original set.
You can use data augmentation on any type of data—this means audio, text, images, video, and so on.
Depending on the type of data in the dataset, the process might look a bit different. For example, for text, we can use sentence shuffling or word replacement, whereas for audio, we can use noise injection or speeding up the audio.
These newly augmented data points can then be used to train various machine learning models to improve not only their performance, but also the generalizability of the existing dataset of a deep learning model. It is also used to ensure the model is being properly trained and that it’s performing as expected.
Why is data augmentation important?
Data augmentation plays a really important role in improving the performance of machine learning models. Training a model on a more diverse dataset has a ton of advantages, such as preventing overfitting, eliminating imbalanced datasets, and allowing more accurate machine learning results.
Overfitting is where a model becomes too tuned to the training data and doesn’t perform well on unseen data, and imbalanced datasets can sway a model’s performance if the data points are skewed in one way or another. Data augmentation can help fix these really common problems that can heavily impact a model's performance if ignored.
Let’s say, for example, you are training a model for sentiment analysis (understanding whether text is positive or negative) with a dataset of five hundred sentences. Four hundred of these sentences are positive and only one hundred are negative. The model’s performance will be skewed because it is majorly trained on positive sentences and may not understand how to recognize a negative sentence. Let’s say we have run out of sentences to come up with ourselves. Data augmentation can help us pad our dataset with new sentences that fall into the negative category to create an even bigger, balanced dataset that will perform more accurately.
Implementing data augmentation
There are various libraries and frameworks that help provide super convenient tools that can help you implement data augmentation on your datasets. Some Python libraries such as TensorFlow, Keras and PyTorch actually offer built-in data augmentation capabilities like `ImageDataGenerator` and `torchvision.transforms`. Both of these libraries let users easily apply transformations to their datasets when they’re training their models.
This involves creating new data points from data that already exists, which could involve incorporating small changes to data or using machine learning models to create new data points in the gaps of the original dataset to amplify it.
Some super common techniques are geometric transformations, like flipping, translation, rotation, or noise insertion, and color space transformations, such as changing RGB color channels or intensifying any existing color.
For image data, TensorFlow actually provides tons of preprocessing layers specifically for data augmentation, such as `tf.keras.layers.RandomContrast`, `tf.keras.layers.RandomCorp`, `tf.keras.layers.RandomZoom`, and more.
One example of this, in Keras, is that you can utilize data augmentation using the ImageDataGenerator class. Here is a sample code snippet showing how to properly apply data augmentation in Keras:
This code snippet shows `rotation_range` defining the range within to randomly rotate images, `width_shift_range` and `height_shift_range` define the range within to randomly translate pictures vertically or horizontally, and `horizontal_flip` allows the data generator to randomly flip half of the images in the dataset horizontally.
When using data augmentation, it is super important to meet a balance between creating enough augmented data points to supplement the dataset without completely compromising the original data. It is crucial to keep the integrity and the representativeness of the original data while still using data augmentation to generate diverse training samples.
Common data augmentation techniques
In this section, we will discuss some of the more commonly used techniques for data augmentation.
Let’s first discuss image augmentation. This is a widely used technique to create new images by applying different transformations to the original images. Some of the most common techniques are rotation, flipping, scaling, translation, shearing, and zooming.
Rotation is a technique involving rotating the image by a certain angle. This allows the model to become invariant to various orientations of objects inside of the image. Flipping is where the image is mirrored, either horizontally or vertically. It helps to teach the model that objects can be in different positions and still be the same object. Scaling is simply resizing the image. Translation is when the image is shifted either horizontally or vertically. Shearing means skewing the image along one axis. Zooming helps either zoom the image in or out.
The second one to talk about is text augmentation. This is an important data augmentation method involving creating new text samples through applying a multitude of transformations to the original text. Some of the common techniques are synonym replacement, random deletion, random insertion, random swap, and random masking.
These are super beneficial because they help replace words with synonyms, randomly delete or insert words, and even randomly swap and mask (hide) other words. All these techniques help to include variations in the dataset and increase not only noise but also the diversity of the training dataset.
The third one is audio augmentation. This involves generating new audio samples by incorporating various transformations to the original audio data. Some of the most common techniques are time stretching, pitch shifting, noise injection, speed perturbation, and amplitude scaling. These require changing the duration of the audio sample with pitch affection versus not incorporating pitch affection, injecting random noise into the audio sample, speeding up the audio, and even adjusting the volume of the audio.
Advanced techniques for data augmentation
We’ve gone over some basic data augmentation techniques, like flipping, rotating, and scaling, but advanced data augmentation methods can further enhance the diversity and quality of our augmented data.
Some of these techniques include:
Cutout augmentation
Cutout augmentation is when randomly selected rectangular areas from an image are replaced with zeros or random noise. It is super useful for object detection and image classification tasks.
By using this technique, we force the model to focus on relevant features and in turn make it more robust to noise in real-world scenarios.
Mixup augmentation
Mixup augmentation is a super useful technique that creates new data points by linearly combining pairs of already existing data points and their corresponding labels. This technique can actually help regularize the model as well.
This provides a way of data smoothing by creating samples from the convex hull of the original samples, which can improve the model’s ability to handle disturbances.
Style transfer augmentation
Typically used for image datasets, style transfer augmentation involves transferring the style or any visual aspects of one image to another while saving the content of the augmented image. This technique actually uses deep learning models, such as convolutional neural networks (CNNs), to extract style and content features from various images.
By doing this and combining the features of a content image with the style of a reference image, style transfer can actually generate new and diverse sets of images that enhance the variability of the data collection in deep learning models.
Generative adversarial networks (GAN) augmentation
Generative adversarial networks (GANs) are a class of neural networks that hold a generator and a discriminator. This type of augmentation uses the power of GANs to create fake data samples and new data points that copy the characteristics of the original data in a training set.
The generator actually learns to produce samples that are almost identical to the original data, while the discriminator learns the difference between real and fake samples.
This type of augmentation actually helps augment the training set with high-quality fake samples, which in turn can help increase the diversity and volume of the data available when training a model.
Contextual data augmentation
This type of augmentation actually focuses on changing the original data by taking into account the context or the very specific attributes of the data samples in the training set. An example of this is in natural language processing tasks where contextual data augmentation techniques like word replacement, insertion, or deletion can actually be used to create new sentences with different but similar meanings, with varied phrasings.
Along the same lines, for time series data, contextual augmentation can be injecting noise specific to the underlying patterns located in the data. By thinking about the context, contextual data augmentation can help create very realistic variations that correlate with the intrinsic characteristics of the training data.
These different and advanced techniques for data augmentation can help give additional options to create diverse and hyper-realistic training sets. By using these techniques, machine learning models can actually achieve higher performance, improved generalization, and a higher robustness in data augmentation work.
It is crucial for data scientists and those involved in the industry to be aware of these various techniques and experiment with them to choose the most suitable and appropriate approaches for their specific tasks and datasets.
Data augmentation has evolved as a way of enhancing the capabilities of machine learning models to create new data points, and in turn, it offers a ton of advantages across various domains for deep learning.
Let’s go ahead and dive into the benefits, challenges, and practical applications that truly make data augmentation an indispensable tool in the world of artificial intelligence and deep learning.
Benefits of data augmentation
There are some really great benefits to data augmentation when it comes to utilizing it to help diversify your datasets. Some of these benefits include improving your model’s prediction accuracy, enriching the training data by adding more varied samples to the data collection process, mitigating data overfitting, and preventing data privacy issues.
These are just some of the incredible benefits, but there are definitely more.
Challenges of data augmentation
There are a few challenges to data augmentation, one of them being that the augmented data sets may not be of great quality. This means companies need to ensure they are checking the datasets and not just blindly trusting the augmentation process. Another challenge is that this field is fairly new. This means the tools used are constantly evolving and companies need to ensure they are conducting the proper research and keeping up with any updates. Biases are a huge concern, as well. Any biases that are present in real datasets will also be in the augmented datasets and they may skew the model incorrectly.
Use cases and examples
Augmentations are most commonly used in image recognition and natural language processing since they enhance the performance of these models. One of the fields where data augmentation is prevalent is in medical imaging. Data augmentation can help address challenges such as small datasets and data privacy regulations, and diagnose rare diseases.
Best practices
Data augmentation is an incredible tool for enhancing model performance, but in order to receive the results most data scientists are looking for, it’s necessary to adhere to certain best practices as it’ll help you get the most out of your augmentation and your deep learning models. Some of these best practices are:
- Selecting appropriate augmentations: Be sure that your choice of augmentations is appropriate with the task at hand. For example, using Random Erasing in face detection might lead to poor results if the augmentation randomly erases the face.
- Avoid excessive augmentation sequences: Using too many augmentations in a single sequence might create data points that are way too different from your original dataset. This can compromise the relevance of the augmented data to your training or testing objectives.
- Validate augmented data: Be sure to check and validate your datasets before you use it! Take a look at any augmented images and text, or listen to any converted audio samples. It’s best to be sure your augmented data is on track with what you’re looking for before running the risk of getting skewed results.
By following these practices, you can harness the full potential of data augmentation while ensuring your deep learning model is dealing with proper data.
Tools
Luckily for us, there are a huge range of open-source tools that are designed to help out your data augmentation journey. Some of the most popular tools are PyTorch, Augmentor, and Albumentations. All of these are Python-based and they allow for image transformations, perspective skewing, distortions, cropping, and much more.
There is a range of open-source tools in this section designed to elevate your data augmentation game and optimize model performance.
The great thing about these tools is that they offer various augmentation options, meaning you have a ton of flexibility when it comes to augmentation with your data.
Conclusion
Data augmentation is crucial for those using machine learning models. Data diversity plays a huge role as it’s necessary to have a wide range of data available for the models to learn from. By incorporating data augmentation and expanding our datasets, we can equip our models with the adaptability to navigate real-world scenarios with ease.