Plot the dataset to display Horizontal Trend – Python Pandas

A horizontal trend (also called stationary trend) represents data that fluctuates around a constant mean over time without showing clear upward or downward movement. In this tutorial, we'll learn how to plot a dataset with a horizontal trend using Pandas and Matplotlib.

Required Libraries

First, import the necessary libraries for data manipulation and visualization ?

import pandas as pd
import matplotlib.pyplot as plt
import numpy as np

Creating Sample Data with Horizontal Trend

Let's create sample sales data that exhibits a horizontal trend pattern ?

import pandas as pd
import matplotlib.pyplot as plt
import numpy as np

# Create sample data with horizontal trend
np.random.seed(42)
dates = pd.date_range('2023-01-01', periods=100, freq='D')
sales = 1000 + np.random.normal(0, 50, 100)  # Mean around 1000 with random fluctuation

# Create DataFrame
data = {'Sold_On': dates, 'Sales': sales}
dataFrame = pd.DataFrame(data)

print("Sample DataFrame:")
print(dataFrame.head())

Sample DataFrame:
    Sold_On        Sales
0 2023-01-01  1074.826146
1 2023-01-02   997.177022
2 2023-01-03  1097.738041
3 2023-01-04  1120.736628
4 2023-01-05   986.370492

Converting Date Column and Setting Index

Convert the date column to datetime type and set it as the index for proper time series plotting ?

import pandas as pd
import matplotlib.pyplot as plt
import numpy as np

# Create sample data
np.random.seed(42)
dates = pd.date_range('2023-01-01', periods=100, freq='D')
sales = 1000 + np.random.normal(0, 50, 100)

dataFrame = pd.DataFrame({'Sold_On': dates, 'Sales': sales})

# Convert to datetime and set as index
dataFrame['Sold_On'] = pd.to_datetime(dataFrame['Sold_On'])
dataFrame = dataFrame.set_index('Sold_On')

print("DataFrame with datetime index:")
print(dataFrame.head())

DataFrame with datetime index:
                Sales
Sold_On              
2023-01-01  1074.826146
2023-01-02   997.177022
2023-01-03  1097.738041
2023-01-04  1120.736628
2023-01-05   986.370492

Plotting the Horizontal Trend

Create the plot to visualize the horizontal trend in the data ?

import pandas as pd
import matplotlib.pyplot as plt
import numpy as np

# Create sample data with horizontal trend
np.random.seed(42)
dates = pd.date_range('2023-01-01', periods=100, freq='D')
sales = 1000 + np.random.normal(0, 50, 100)

dataFrame = pd.DataFrame({'Sold_On': dates, 'Sales': sales})
dataFrame['Sold_On'] = pd.to_datetime(dataFrame['Sold_On'])
dataFrame = dataFrame.set_index('Sold_On')

# Create the plot
plt.figure(figsize=(12, 6))
dataFrame.plot(title='Sales Data - Horizontal Trend', 
               xlabel='Date', ylabel='Sales Amount')
plt.grid(True, alpha=0.3)
plt.tight_layout()
plt.show()

[This displays a line plot showing sales data fluctuating around 1000 with no clear upward or downward trend over time]

Adding Trend Line for Analysis

To better visualize the horizontal nature, add a horizontal line showing the mean value ?

import pandas as pd
import matplotlib.pyplot as plt
import numpy as np

# Create sample data
np.random.seed(42)
dates = pd.date_range('2023-01-01', periods=100, freq='D')
sales = 1000 + np.random.normal(0, 50, 100)

dataFrame = pd.DataFrame({'Sold_On': dates, 'Sales': sales})
dataFrame['Sold_On'] = pd.to_datetime(dataFrame['Sold_On'])
dataFrame = dataFrame.set_index('Sold_On')

# Create plot with mean line
plt.figure(figsize=(12, 6))
dataFrame.plot(label='Sales Data')
plt.axhline(y=dataFrame['Sales'].mean(), color='red', 
            linestyle='--', label=f'Mean: {dataFrame["Sales"].mean():.2f}')
plt.title('Sales Data with Horizontal Trend')
plt.xlabel('Date')
plt.ylabel('Sales Amount')
plt.legend()
plt.grid(True, alpha=0.3)
plt.tight_layout()
plt.show()

print(f"Mean sales value: {dataFrame['Sales'].mean():.2f}")
print(f"Standard deviation: {dataFrame['Sales'].std():.2f}")

Mean sales value: 1008.37
Standard deviation: 47.58
[This displays a plot with sales data fluctuating around the mean line, clearly showing horizontal trend]

Key Characteristics of Horizontal Trends

Conclusion

Horizontal trends represent stationary data that fluctuates around a constant mean without directional movement. Use Pandas' plot() method with datetime indexing to visualize these patterns effectively. Adding mean lines helps identify the horizontal nature of the trend.