You can check if a time-series belongs to last year using pandas by first converting the time-series into a datetime object. Once the time-series is in datetime format, you can extract the year from each date using the dt.year attribute. Finally, you can compare the extracted year to the previous year (current year - 1) to determine if the time-series belongs to last year.

## What is the difference between a date and a datetime object in Pandas?

In Pandas, a date object represents a specific date with no time component, while a datetime object represents a specific date and time.

A date object in Pandas is typically of the type 'datetime64[D]', where 'D' signifies that it represents a date. It does not store any time information and is often used for analyzing data based on dates only.

A datetime object, on the other hand, is typically of the type 'datetime64[ns]', where 'ns' signifies that it includes nanoseconds precision. It stores both the date and time components and is often used for analyzing data based on specific date and time information.

In summary, a date object in Pandas represents a specific date only, while a datetime object represents a specific date and time.

## What is the role of lag plots in time-series analysis in Pandas?

Lag plots are useful in time-series analysis in Pandas because they help us understand the autocorrelation of a time series. Autocorrelation is the correlation of a series with a delayed copy of itself (lagged values). By creating a lag plot, we can visually inspect how correlated a time series is with its lagged values, which can help us identify potential patterns or relationships in the data.

Lag plots can also be used to check for randomness in the data and to detect any seasonality or trends. In addition, lag plots can help us determine the appropriate lag order for models such as autoregressive integrated moving average (ARIMA) models.

Overall, lag plots play an important role in time-series analysis in Pandas by providing valuable insights into the autocorrelation structure of a time series and helping us make informed decisions about modeling and forecasting.

## How to filter time-series data in Pandas based on a specific date range?

You can filter time-series data in Pandas based on a specific date range by using the `pd.DataFrame.loc`

method and providing a condition for the date range. Here's an example:

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import pandas as pd # Create a sample DataFrame with time-series data data = {'date': pd.date_range(start='2022-01-01', periods=10, freq='D'), 'value': [10, 20, 30, 40, 50, 60, 70, 80, 90, 100]} df = pd.DataFrame(data) # Set the 'date' column as the index df.set_index('date', inplace=True) # Filter the DataFrame based on a specific date range start_date = '2022-01-03' end_date = '2022-01-06' filtered_df = df.loc[start_date:end_date] print(filtered_df) |

In this example, we created a sample DataFrame with time-series data and set the 'date' column as the index. We then specified a start date and an end date for the date range we want to filter. Finally, we used the `loc`

method to filter the DataFrame based on the specified date range and stored the filtered data in a new DataFrame called `filtered_df`

.

You can modify the start_date and end_date variables to filter the DataFrame based on your desired date range.

## What is the concept of time-series stationarity in Pandas?

Time-series stationarity in Pandas refers to the property of a time series where the statistical properties, such as mean, variance, and autocorrelation, remain constant over time. A stationary time series is one where the data points are not dependent on when they are observed, making it easier to make predictions and identify trends in the data.

In Pandas, you can check for time-series stationarity using statistical tests such as the Augmented Dickey-Fuller test or visualizations such as a plot of the time series data. If a time series is not stationary, you may need to perform transformations such as differencing or detrending to make it stationary before applying predictive models or analysis.