Machine learning model training: how different approaches to machine learning shape the training process
Let’s start with this: there’s no one-size-fits-all approach to machine learning. The way you train a machine learning model depends on the nature of your data and the outcomes you’re aiming for.
Let’s take a quick look at four key approaches to machine learning and see how each shapes the training process.
Supervised learning
In supervised learning, the algorithm is trained on a labeled dataset, learning to map input data to the correct output. An engineer guides a model through a set of solved problems before the model can tackle new ones on its own.
Example: Consider a supervised learning model tasked with classifying images of cats and dogs. The labeled dataset comprises images tagged with corresponding labels (cat or dog). The model refines its parameters to accurately predict the labels of new, unseen images.
Unsupervised learning
Here, to the contrary, the algorithm dives into unlabeled data and seeks patterns and relationships on its own. It groups similar data points and discovers hidden structures.
Example: Think of training a machine learning model for customer clusterization in an e-commerce dataset. The model goes through customer data and discerns distinct customer clusters based on their purchasing behavior.
Semi-supervised learning
Semi-supervised learning is the middle ground that combines elements of both supervised and unsupervised learning. With a small amount of labeled data and a larger pool of unlabeled data, the algorithm strikes a balance. It’s the pragmatic choice when fully labeled datasets are scarce.
Example: Imagine a medical diagnosis scenario where labeled data (cases with known outcomes) is limited. Semi-supervised learning would leverage a combination of labeled patient data and a larger pool of unlabeled patient data, enhancing its diagnostic capabilities.
Reinforcement learning
Reinforcement learning is an algorithmic equivalent of trial and error. A model interacts with an environment, making decisions and receiving feedback in the form of rewards or penalties. Over time, it refines its strategy to maximize cumulative rewards.
Example: Consider training a machine learning model for an autonomous drone. The drone learns to navigate through an environment by receiving rewards for successful navigation and penalties for collisions. Over time, it refines its policy to navigate more efficiently.
While each machine learning approach requires a uniquely tailored sequence and emphasis on certain steps, there exists a core set of steps that are broadly applicable across various methods.
In the next section, we are walking you through that sequence.
Machine learning model training step by step
Identifying opportunities and defining project scope
The step involves not just deciphering the business problem at hand but also pinpointing the opportunities where machine learning can yield its transformative power.
Start by engaging with key stakeholders, including decision-makers and domain experts, to gain a comprehensive understanding of the business challenges and objectives.
Next, clearly articulate the specific problem you aim to address by training a machine learning model and ensure it aligns with broader business goals.
When doing so, beware of ambiguity. Ambiguous problem statements can lead to misguided solutions. It’s crucial to clarify and specify the problem to avoid misdirection during subsequent stages. For example, go for “increase user engagement on the mobile app by 15% through personalized content recommendations within the next quarter” instead of “increase user engagement”—it’s quantified, focused, and measurable.
The next step that you can take as early as at the scope definition stage is assessing the availability and quality of relevant data.
Identify potential data sources that can be leveraged to solve the problem. Say, you want to predict customer churn in a subscription-based service. You will have to assess customer subscription records, usage logs, interactions with support teams, and billing history. Apart from that, you could also turn to social media interactions, customer feedback surveys, and external economic indicators.
Finally, evaluate the feasibility of applying machine learning techniques to the identified problem. Consider technical (e.g., computational capacity and processing speed of the existing infrastructure), resource (e.g., available expertise and budget), and data-related (e.g., data privacy and accessibility considerations) constraints.
Data discovery, validation, and preprocessing
The foundation of successful machine learning model training lies in high-quality data. Let’s explore strategies for data discovery, validation, and preprocessing.
Data discovery
Before diving into ML model training, it’s essential to gain a profound understanding of the data you have. This involves exploring the structure, formats, and relationships within the data.
What does data discovery entail exactly?
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Exploratory data analysis (EDA), where you unravel patterns, correlations, and outliers within the available dataset, as well as visualize key statistics and distributions to gain insights into the data.
Imagine a retail business aiming to optimize its pricing strategy. In the EDA phase, you delve into historical sales data. Through visualization techniques such as scatter plots and histograms, you uncover a strong positive correlation between promotional periods and increased sales. Additionally, the analysis reveals outliers during holiday seasons, indicating potential anomalies requiring further investigation. Thus, EDA allows for grasping the dynamics of sales patterns, correlations, and outlier behavior.
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Feature identification, where you identify features that contribute meaningfully to the problem at hand. You also consider the relevance and significance of each feature for attaining the set business goal.
Building on the example above, feature identification may involve recognizing which aspects impact sales. Through careful analysis, you may identify features such as product categories, pricing tiers, and customer demographics as potential contributors. Then you consider the relevance of each feature. For instance, you note that the product category may have varying significance during promotional periods. Thus, feature identification ensures that you train the machine learning model on attributes with a meaningful impact on the desired outcome.
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Data sampling, where you utilize sampling techniques to get a representative subset of the data for initial exploration. For the retail business from the example above, data sampling becomes essential. Say, you employ random sampling to extract a representative subset of sales data from different time periods. This way, you ensure a balanced representation of normal and promotional periods.
Then you may apply stratified sampling to ensure that each product category is proportionally represented. By exploring this subset, you gain preliminary insights into sales trends, which enables you to make informed decisions about subsequent phases of the machine learning model training journey.
Data validation
The importance of robust data validation for machine learning model training cannot be overstated. It ensures that the information fed into the model is accurate, complete, and consistent. It also helps foster a more reliable model and helps mitigate bias.
At the data validation stage, you thoroughly assess data integrity and identify any discrepancies or anomalies that could impact model performance. Here are the exact steps to take:
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Data quality checks, where you (1) search for missing values across features and identify appropriate strategies for their removal; (2) ensure consistency in data format and units, minimizing discrepancies that may impact model training; (3) identify and handle outliers that could skew model training; and (4) verify the logical adequacy of the data.
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Cross-verification, where you cross-verify data against domain knowledge or external sources to validate its accuracy and reliability.
Data preprocessing
Data preprocessing ensures that the model is trained on a clean, consistent, and representative dataset, enhancing its generalization to new, unseen data. Here’s what you do to achieve that:
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Handling missing data: identify missing values and implement strategies such as imputation or removal based on the nature of the data and the business problem being solved.
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Detecting and treating outliers: employ statistical methods to identify and handle outliers, ensuring they do not impact the model’s learning process.
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Normalization, standardization: scale numerical features to a standard range (e.g., using Z-score normalization), ensuring consistency and preventing certain features from dominating others.
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Encoding: convert data to a consistent format (e.g., through one-hot encoding or word embeddings).
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Feature engineering: derive new features or modify existing ones to enhance the model’s ability to capture relevant patterns in the data.
When preparing data for machine learning model training, it is important to strike a balance between retaining valuable information within the dataset and addressing the inherent imperfections or anomalies present in the data. Striking the wrong balance may lead to the inadvertent loss of valuable information, limiting the model’s ability to learn and generalize.
Adopt strategies that address imperfections while minimizing the loss of meaningful data. This may involve careful outlier treatment, selective imputation, or considering alternative encoding methods for categorical variables.
Data engineering
In cases where data is insufficient, data engineering comes into play. You can compensate for the lack of data through techniques like data augmentation and synthesis. Let’s dive into the details:
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Data augmentation: involves creating new variations or instances of existing data by applying various transformations without altering the inherent meaning. For instance, for image data, augmentation could include rotation, flipping, zooming, or changing brightness. For text data, variations might involve paraphrasing or introducing synonyms. Thus, by artificially expanding the dataset through augmentation, you introduce the model to a more diverse range of scenarios, improving its ability to perform on unseen data.
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Data synthesis: entails generating entirely new data instances that align with the characteristics of the existing dataset. Synthetic data can be created using generative AI models, simulation, or leveraging domain knowledge to generate plausible examples. Data synthesis is particularly valuable in situations where obtaining more real-world data is challenging.
Choosing an optimal algorithm
The data work is done. The next stage in the process of machine learning model training is all about algorithms. Choosing an optimal algorithm is a strategic decision that influences the performance and precision of your future model.
There are several popular machine learning algorithms, each appropriate for a specific set of tasks, namely:
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Linear regression: applicable for predicting a continuous outcome based on input features. It is ideal for scenarios where a linear relationship exists between the features and the target variable, for example, predicting a house price based on features like square footage, number of bedrooms, and location.
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Decision trees: capable of handling both numerical and categorical data, making them suitable for tasks requiring clear decision boundaries, for instance, determining if an email is spam or not based on such features as sender, subject, and content.
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Random forest: ensemble learning approach that combines multiple decision trees for higher accuracy and robustness, making it effective for complex problems, for example, predicting customer churn using a combination of historical usage data and customer demographics.
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Support Vector Machines (SVM): effective for scenarios where clear decision boundaries are crucial, especially in high-dimensional spaces like medical imaging. An example of a task SVMs may be applied to includes classifying medical images as cancerous or non-cancerous based on various features extracted from the images.
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K-Nearest Neighbors (KNN): relying on proximity, KNN makes predictions based on the majority class or average of nearby data points. This makes KNN suitable for collaborative filtering in recommendation systems, where it can suggest movies to a user based on the preferences of users with a similar viewing history.
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Neural networks: excel in capturing intricate patterns and relationships, making them applicable to diverse complex tasks, including image recognition and natural language processing.
Here are the factors that influence the choice of an algorithm for machine learning model training:
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Nature of the problem: the type of problem, whether it’s classification, regression, clustering, or something else.
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Size and complexity of the dataset: large datasets may benefit from algorithms that scale well, while complex data structures may require more sophisticated models.
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Interpretability requirements: some algorithms offer more interpretability, which is crucial for scenarios where understanding model decisions is paramount.
Machine learning model training
At the model training stage, you train and tune the algorithms for optimal performance. In this section, we will guide you through the essential steps of the model training process.
Start by dividing your dataset into three parts: training, validation, and testing sets.
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Training set: this subset of data is the primary source for teaching the model. It’s used to train the ML model, allowing it to learn patterns and relationships between inputs and outputs. Typically, the training set comprises the largest part of available data.
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Validation set: this data set helps evaluate the model’s performance during training. It’s used to fine-tune hyperparameters and assess the model’s generalization ability.
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Testing set: this data set serves as the final examination for the model. It comprises new data that the model has not encountered during training or validation. The testing set provides an estimate of how the model might perform in real-world scenarios.
After running the algorithms through the testing data set, you get an initial understanding of the model’s performance and go onto hyperparameter tuning.
Hyperparameters are predefined configurations that guide the learning process of the model. Some examples of hyperparameters may be the learning rate, which controls the step size during training, or the depth of a decision tree in a random forest. Adjusting the hyperparameters helps find the perfect “setting” for the model.
Model evaluation and validation
To ensure the optimal performance of the model, it is important to evaluate it against the set metrics. Depending on the task at hand, you may opt for a specific set of metrics. The ones commonly used in machine learning model training span:
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Accuracy quantifies the overall correctness of the model’s predictions and illustrates its general proficiency.
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Precision and recall, where the former hones in on the accuracy of positive predictions, ensuring that whenever the model claims a positive outcome, it does so correctly, and the latter gauges the model’s ability to capture all positive instances in the dataset.
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F1 score seeks to strike a balance between precision and recall. It provides a single numerical value that captures the model’s performance. As precision and recall often show a trade-off (think: improving one of these metrics typically comes at the expense of the other), the F1 score offers a unified measure that considers both aspects.
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AUC-ROC, or the area under the receiver operating characteristic, reflects the model’s ability to distinguish between positive and negative classes.
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“Distance metrics” quantify the difference, or “distance” between the predicted values and the actual values. Examples of “distance metrics” are Mean Squared Error (MSE), Mean Absolute Error (MAE), R-squared, and others.
Model productization/deployment and scaling
Once a machine learning model has been trained and validated, the next critical step is deployment—putting the model into action in a real-world environment. This involves integrating the model into the existing business infrastructure.
The key aspects of model deployment to be aware of span:
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Scalability
The deployed model should be designed to handle varying workloads and adapt to changes in data volume. Scalability is crucial, especially in scenarios where the model is expected to process large amounts of data in real time.
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Monitoring and maintenance
Continuous monitoring is essential after the deployment. This involves tracking the model’s performance in real-world conditions, detecting any deviations or degradation in accuracy, and addressing issues promptly. Regular maintenance ensures the model remains effective as the business environment evolves.
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Feedback loops
Establishing feedback loops is vital for continuous improvement. Collecting feedback from the model’s predictions in the real world allows data scientists to refine and enhance the model over time.
Overcoming challenges in ML model training, at an example
Let’s break down the specifics of training a machine learning model by exploring a real-life example. Below, we document our journey in creating a revolutionary smart fitness mirror with AI capabilities, hoping to give you insights into the practical side of machine learning.
Let us share a bit of context first.
As the pandemic shuttered gyms and fueled the rise of home fitness, our client envisioned a game-changing solution—a smart fitness mirror that acts as a personal coach. It captures users’ motions, provides real-time guidance, and crafts personalized training plans.
To bring this functionality to life, we designed and trained a proprietary ML model.
Due to the intricate nature of the solution, the ML model training process was not an easy one. We’ve stumbled across a few challenges that we, however, successfully addressed. Let’s have a look at the most noteworthy ones.
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Ensuring the diversity of training data
To train a high-performing model, we had to ensure that the training dataset was diverse, representative, and free from bias. To achieve that, our team implemented data preprocessing techniques, including outlier detection and removal.
Additionally, to compensate for the potential gap in the dataset and enhance its diversity, we shot custom videos showcasing people exercising in various environments, under different light conditions, and with diverse exercise equipment.
By augmenting our dataset with this extensive video footage, we enriched the model’s understanding, enabling it to adapt more effectively to real-world scenarios.
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Navigating the algorithmic complexity of the model
Another challenge we encountered was designing and training a deep learning model that is capable enough to accurately estimate users’ poses and and track and interpret their motions.
We implemented depth sensing to capture motion based on anatomical landmarks. This was no simple feat; it required precise processing and landmark recognition.
After an initial round of training, we continued to fine-tune the algorithms by incorporating advanced computer vision techniques, such as skeletonization (think: transforming the user’s silhouette into a simplified skeletal structure for efficient landmark identification) and tracking (ensuring consistency in landmark recognition over time, vital for maintaining accuracy throughout the dynamic exercise).
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Ensuring seamless IoT device connectivity and integration
As the fitness mirror does not only track body movements but also the weights users train with, we introduced wireless adhesive sensors attached to individual equipment pieces.
We had to ensure uninterrupted connectivity between the sensors and the mirror, as well as enable real-time data synchronization. For that, we implemented optimized data transfer protocols and developed error-handling strategies to address potential glitches in data transmission. Additionally, we employed bandwidth optimization techniques to facilitate swift communication crucial for real-time synchronization during dynamic exercises.
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Implementing voice recognition
The voice recognition functionality in the fitness mirror added an interactive layer, allowing users to control and engage with the device through voice commands.
To enable users to interact with the system, we implemented a voice-activated microphone with a fixed list of fitness-related commands and voice recognition technology that can learn new words and understand new prompts given by the user.
The challenge was that users often exercised in home environments with ambient noise, which made it difficult for the voice recognition system to accurately understand commands. To tackle this challenge, we implemented noise cancellation algorithms and fine-tuned the voice recognition model to enhance accuracy in noisy conditions.
Future trends in ML model training
The landscape of machine learning is evolving, and one notable trend that promises to reshape the ML model training process is automated machine learning, or AutoML. AutoML offers a more accessible and efficient approach to developing ML models.
It allows automating much of the workflow described above, allowing even those without extensive ML expertise to harness the power of machine learning.
Here’s how AutoML is set to influence the ML training process:
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Accessibility for all: AutoML democratizes machine learning by simplifying the complexities involved in model training. Individuals with diverse backgrounds, not just seasoned data scientists, can leverage AutoML tools to create powerful models.
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Efficiency and speed: The traditional ML development cycle can be resource-intensive and time-consuming. AutoML streamlines this process, automating tasks like feature engineering, algorithm selection, and hyperparameter tuning. This accelerates the model development lifecycle, making it more efficient and responsive to business needs.
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Optimization without expertise: AutoML algorithms excel at optimizing models without the need for deep expertise. They iteratively explore different combinations of algorithms and hyperparameters, seeking the best-performing model. This not only saves time but also ensures that the model is fine-tuned for optimal performance.
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Continuous learning and adaptation: AutoML systems often incorporate aspects of continuous learning, adapting to changes in data patterns and business requirements over time. This adaptability ensures that models remain relevant and effective in dynamic environments.
