Time series data is a sequence of data points indexed in time order. It is a common type of data format in many fields such as finance, economics, ecology, neuroscience, and physics. Pandas is a powerful tool for manipulating this kind of data.
In this tutorial, you will learn how to handle time series data using Pandas. We will cover how to import time series data, manipulate and analyze it, and visualize it.
Prerequisites: Basic Python programming, a working installation of Python and Pandas.
Time series data handling with Pandas involves four main steps: importing data, converting to datetime format, manipulating and analyzing the data, and finally visualizing the data. We will go through each of these steps in detail.
When working with time series data in Pandas, the DateTimeIndex is the core data structure that allows you to manipulate and analyze the data. It is an optimized index for handling dates and times, providing various built-in functions for easy data manipulation.
Always remember to import the necessary libraries before processing data:
import pandas as pd
Example 1: Importing Time Series Data
Here, we are importing a CSV file with time series data. The parse_dates parameter is used to specify the column containing the date.
# Import data
df = pd.read_csv('timeseries.csv', parse_dates=['date'])
# Print the first 5 rows
print(df.head())
Example 2: Converting to DateTime Format
In this example, we convert a column to datetime format using the pd.to_datetime() function.
# Convert to datetime format
df['date'] = pd.to_datetime(df['date'])
# Set the date column as index
df.set_index('date', inplace=True)
# Print the first 5 rows
print(df.head())
Example 3: Resampling Time Series Data
Resampling involves changing the frequency of your time series observations. We can downsample (reduce the frequency of the samples) or upsample (increase the frequency of the samples).
# Downsample to quarterly data points
df_quarterly = df.resample('Q').mean()
# Upsample to daily data points
df_daily = df.resample('D').ffill()
# Print the first 5 rows of the downsampled dataframe
print(df_quarterly.head())
Example 4: Plotting Time Series Data
Pandas integrates with Matplotlib to provide easy plotting of time series data.
import matplotlib.pyplot as plt
# Plot the dataframe
df.plot()
# Show the plot
plt.show()
In this tutorial, we have learned how to handle time series data using Pandas. We have covered how to import time series data, convert it to datetime format, resample it, and visualize it.
Next steps for learning could be diving deeper into time series analysis techniques, such as decomposition, forecasting, and time series classification.
Exercise 1: Import a time series dataset and convert the date column to datetime format.
Exercise 2: Downsample the data to monthly frequency and calculate the sum of another column for each month.
Exercise 3: Plot the original data and the downsampled data on the same plot.
Solutions:
Solution 1:
df = pd.read_csv('timeseries.csv', parse_dates=['date'])
df['date'] = pd.to_datetime(df['date'])
df.set_index('date', inplace=True)
Solution 2:
df_monthly = df.resample('M').sum()
Solution 3:
df.plot()
df_monthly.plot()
plt.show()
Remember to always experiment with different resampling methods and frequencies to understand the data better. Happy coding!