The code mentioned is using a lambda expression to add a Boolean column to the fires DataFrame, indicating whether a state touches the Pacific Ocean. Let's break it down step-by-step:
1. First, we need to understand what a lambda expression is. In Python, a lambda function is a small anonymous function that can take any number of arguments but can only have one expression. It is usually used when we need a simple function without a name.
2. The lambda expression in this code is used as an argument to the `apply()` function, which is called on the fires DataFrame. The `apply()` function applies a function along an axis of the DataFrame.
3. Inside the lambda expression, we have the logic to determine whether a state touches the Pacific Ocean. It is not explicitly mentioned in the question, but we can assume that the DataFrame contains a column representing the states. We can access this column using the `[]` notation, and then use the `str` accessor to check if the state name contains the string "Pacific". This will return `True` if it does and `False` otherwise.
4. The result of the lambda expression is a new column with Boolean values indicating whether each state touches the Pacific Ocean.
Overall, the lambda expression is used to define a custom logic to add a Boolean column to the fires DataFrame, based on whether a state name contains the string "Pacific".