Understanding Parameters and Hyperparameters

Introduction

An introduction to machine learning (ML) or deep learning (DL) involves understanding two basic concepts: parameters and hyperparameters. When I came across these terms for the first time, I was confused because they were new to me. If you’re reading this, I assume you are in a similar situation too. So let’s explore and understand what these two terms mean.

Overview

• Learn what parameters and hyperparameters are in machine learning and deep learning.
• Know what a model parameter and model hyperparameter is.
• Explore some examples of hyperparameters.
• Understand the differences between parameters and hyperparameters.

What are Parameters and Hyperparameters?

In ML and DL, models are defined by their parameters. Training a model means finding the best parameters to map input features (independent variables) to labels or targets (dependent variables). This is where hyperparameters come into play.

What is a Model Parameter?

Model parameters are configuration variables that are internal to the model and are learned from the training data. For example, weights or coefficients of independent variables in the linear regression model, weights or coefficients of independent variables in SVM, weights and biases of a neural network, and cluster centroids in clustering algorithms.

Example: Simple Linear Regression

We can understand model parameters using the example of Simple Linear Regression:

The equation of a Simple Linear Regression line is given by: y=mx+c

Here, x is the independent variable, y is the dependent variable, m is the slope of the line, and c is the intercept of the line. The parameters m and c are calculated by fitting the line to the data by minimizing the Root Mean Square Error (RMSE).

Key points for model parameters:

• The model uses them to make predictions.
• The model learns them from the data.
• These are not set manually.
• These are crucial for machine learning algorithms.

Example in Python

Here’s an example in Python to illustrate the interaction between hyperparameters and parameters:

import numpy as np
from sklearn.model_selection import train_test_split
from sklearn.linear_model import LogisticRegression
from sklearn.metrics import accuracy_score

# Generating some sample data
X, y = np.arange(10).reshape((5, 2)), range(5)

# Hyperparameters
test_size = 0.2
learning_rate = 0.01
max_iter = 100

# Splitting the data
X_train, X_test, y_train, y_test = train_test_split(X, y, test_size=test_size)

# Defining and training the model
model = LogisticRegression(max_iter=max_iter)
model.fit(X_train, y_train)

# Making predictions
predictions = model.predict(X_test)

# Evaluating the model
accuracy = accuracy_score(y_test, predictions)
print(f'Accuracy: {accuracy}')

In this code:

• Hyperparameters: test_size, max_iter
• Parameters: The weights learned by the LogisticRegression model during training

What is a Model Hyperparameter?

Hyperparameters are parameters explicitly defined by the user to control the learning process.

Key points for model hyperparameters:

• Defined manually by the machine learning engineer.
• Cannot be determined precisely in advance; typically set using rules of thumb or trial and error.
• Examples include the learning rate for training a neural network, K in the KNN algorithm, etc.

Hyperparameter Tuning

Hyperparameters are set before training starts and guide the learning algorithm in adjusting the parameters. For instance, the learning rate (a hyperparameter) determines how much to change the model’s parameters in response to the estimated error each time the model weights are updated.

Hyperparameter Examples

Some common examples of hyperparameters include:

• The ratio for splitting data into training and test sets
• Learning rate for optimization algorithms
• The choice of optimization algorithm (e.g., gradient descent, Adam)
• Activation functions in neural network layers (e.g., Sigmoid, ReLU)
• The loss function used
• Number of hidden layers in a neural network
• Number of neurons in each layer
• Dropout rate in neural networks
• Number of training epochs
• Number of clusters in clustering algorithms
• Kernel size in convolutional layers
• Pooling size
• Batch size

These settings are crucial as they influence how well the model learns from the data.

Personal Insight

It was not easy when I embarked on machine learning to distinguish between parameters and hyperparameters. However, it was worth the time. It is through trial and error that I discovered how tweaking hyperparameters such as the learning rate or number of epochs can have a significant impact on the model’s performance. Little did I know that making adjustments on these particular factors would later determine my level of success. Finding optimal settings for your model indeed requires keen experimentation; there are no shortcuts around this process.

Comparison Between Parameters and Hyperparameters

Conclusion

Understanding parameters and hyperparameters is crucial in ML and DL. Hyperparameters control the learning process, while parameters are the values the model learns from the data. This distinction is vital for tuning models effectively. As you continue learning, remember that choosing the right hyperparameters is key to building successful models.

By having a clear understanding of model parameters and hyperparameters, beginners can better navigate the complexities of machine learning. They can also improve their model’s performance through informed tuning and experimentation. So, happy experimenting!

Frequently Asked Questions

Janvi Kumari

Hi, I am Janvi, a passionate data science enthusiast currently working at Analytics Vidhya. My journey into the world of data began with a deep curiosity about how we can extract meaningful insights from complex datasets.