The correct answer is: B. To reduce the size of the training dataset.
Dimensionality reduction is the process of reducing the number of variables in a dataset while preserving as much of the information as possible. This can be useful for a number of reasons, such as:
- Reducing the computational cost of training and evaluating a model.
- Making it easier to visualize and understand the data.
- Making it possible to apply machine learning algorithms to datasets that would otherwise be too large.
Principal component analysis (PCA) is a popular dimensionality reduction technique. It works by finding a set of orthogonal (i.e., uncorrelated) vectors, called principal components, that capture as much of the variance in the data as possible. The first principal component is the vector that captures the most variance, the second principal component captures the second most variance, and so on.
Once the principal components have been found, the data can be projected onto them. This means that each data point is represented by a new vector, whose components are the projections of the data point onto the principal components. The number of principal components used to project the data can be chosen to trade off between the amount of information that is preserved and the computational cost of working with the projected data.
PCA is a powerful tool that can be used to reduce the size of training datasets, make it easier to visualize and understand data, and make it possible to apply machine learning algorithms to datasets that would otherwise be too large.
Here is a brief explanation of each option:
- A. To increase model interpretability. This is not the primary goal of dimensionality reduction techniques. While dimensionality reduction can sometimes make models easier to interpret, this is not its primary purpose.
- C. To perform unsupervised learning. Dimensionality reduction is a supervised learning technique. It is used to reduce the dimensionality of data that has already been labeled. Unsupervised learning techniques, on the other hand, are used to learn from unlabeled data.
- D. To visualize data relationships. Dimensionality reduction can be used to visualize data relationships, but this is not its primary purpose. The primary purpose of dimensionality reduction is to reduce the dimensionality of data.