Welcome to the beginning of our journey into content-based recommendation systems. In the grand scope of recommendation technologies, these systems play a crucial role. They allow applications to suggest relevant items to users based on various content features, enhancing the user experience through personalization. Imagine a music app recommending songs based on the characteristics of songs that a user has liked or listened to in the past. That's the power of a content-based system!

In this lesson, we will delve into how content features are extracted to create efficient recommendations, setting a solid foundation for more advanced techniques.

Let's start by revisiting the datasets we will be working with: tracks.json and authors.json. These JSON files contain essential information about music tracks and artists, respectively. Here is an example of how this can work:

Note that we link a track to its author using the author_id field.

In Go, we can read JSON files and unmarshal their contents into slices of structs. This allows us to work with the data in a structured way.

First, let's define the structs that match the structure of our JSON data:

Now, let's read the JSON files and unmarshal them into slices of these structs:

After loading, the tracks and authors slices in Go represent tabular data structures, similar to spreadsheets. Each element in the slice is like a row, and each field in the struct is like a column. For example, the data looks like this:

tracks:

authors:

To make meaningful recommendations, we need to combine information about tracks and authors. In Go, we can do this by matching the author_id field in both slices. One efficient way is to build a map from author ID to author struct, and then create a new slice that combines the information.

Let's define a new struct to hold the merged data:

Now, let's merge the data:

After merging, the combined data will look like this:

This merged structure ensures that each track is paired with the corresponding author information. Only records with matching author_id values in both datasets are included, similar to an inner join in tabular data processing.

Content features are specific attributes of data that can be used to calculate recommendations. They provide the basis for comparing items and identifying similarities.

In our example, we’re interested in features such as the number of likes, clicks, full_listens, the number of author_listeners, and the genre. Let's define a new struct to hold only these relevant features:

Now, let's extract these features from the merged data:

This results in a slice of ContentFeatures structs, each containing only the essential features that drive our recommendation logic. By isolating these features, we prepare a tidy dataset that is easy to use for content-based algorithms.

Output:

This output shows a clean list with only the essential features that drive our recommendation logic.

Note:
While features like Likes, Clicks, and are already numeric and can be used directly in similarity calculations or machine learning models, categorical features such as (and, if used, ) are represented as strings. Most downstream similarity algorithms and models require these categorical fields to be converted into numeric representations—such as one-hot encoding, label encoding, or learned embeddings—before they can be used effectively. We will address how to handle these categorical features in later units.

In this lesson, we've covered the initial steps in building a content-based recommendation system. Starting from loading the data, merging datasets, and extracting relevant content features, you've gained skills crucial for moving forward with more comprehensive recommendations.

The next step for you is to apply this knowledge in practice exercises on CodeSignal, where you will put into practice what you've just learned. Remember, the skills acquired here are foundational, paving the way for more sophisticated and personalized recommendation systems. Keep exploring, and enjoy the process of crafting tailored experiences for your future users!