Introduction

Streamlit has revolutionized the way data scientists and developers create web applications in Python. Its simplicity and power make it an excellent choice for building data-driven apps. When it comes to visualizations, Streamlit offers built-in support for various charting libraries, including Matplotlib and Plotly. In this blog post, we'll explore how to integrate these popular visualization tools into your Streamlit apps, enhancing their visual appeal and interactivity.

Matplotlib Integration

Matplotlib is a widely-used plotting library in Python, known for its flexibility and extensive customization options. Let's start by integrating a simple Matplotlib chart into a Streamlit app.

First, make sure you have the necessary libraries installed:

pip install streamlit matplotlib

Now, let's create a basic line plot:

import streamlit as st
import matplotlib.pyplot as plt
import numpy as np

def create_matplotlib_chart():
    x = np.linspace(0, 10, 100)
    y = np.sin(x)
    
    fig, ax = plt.subplots()
    ax.plot(x, y)
    ax.set_title('Sine Wave')
    ax.set_xlabel('X-axis')
    ax.set_ylabel('Y-axis')
    
    return fig

st.title('Matplotlib in Streamlit')
st.pyplot(create_matplotlib_chart())

In this example, we define a function create_matplotlib_chart() that generates a simple sine wave plot using Matplotlib. We then use st.pyplot() to display the chart in our Streamlit app.

Adding Interactivity with Matplotlib

While Matplotlib isn't inherently interactive, we can add some basic interactivity using Streamlit's widgets. Let's modify our example to allow users to adjust the frequency of the sine wave:

import streamlit as st
import matplotlib.pyplot as plt
import numpy as np

def create_interactive_matplotlib_chart(frequency):
    x = np.linspace(0, 10, 100)
    y = np.sin(frequency * x)
    
    fig, ax = plt.subplots()
    ax.plot(x, y)
    ax.set_title(f'Sine Wave (Frequency: {frequency})')
    ax.set_xlabel('X-axis')
    ax.set_ylabel('Y-axis')
    
    return fig

st.title('Interactive Matplotlib in Streamlit')
frequency = st.slider('Frequency', 0.1, 5.0, 1.0, 0.1)
st.pyplot(create_interactive_matplotlib_chart(frequency))

Now, users can adjust the frequency of the sine wave using a slider, and the chart updates in real-time.

Plotly Integration

Plotly is another powerful visualization library that offers interactive charts out of the box. Let's see how we can integrate Plotly into our Streamlit app.

First, install the required libraries:

pip install streamlit plotly

Now, let's create a simple scatter plot using Plotly:

import streamlit as st
import plotly.graph_objects as go
import numpy as np

def create_plotly_chart():
    x = np.random.randn(100)
    y = np.random.randn(100)
    
    fig = go.Figure(data=go.Scatter(x=x, y=y, mode='markers'))
    fig.update_layout(title='Random Scatter Plot',
                      xaxis_title='X-axis',
                      yaxis_title='Y-axis')
    
    return fig

st.title('Plotly in Streamlit')
st.plotly_chart(create_plotly_chart())

In this example, we create a random scatter plot using Plotly's go.Scatter and display it using st.plotly_chart().

Enhancing Interactivity with Plotly

Plotly charts are inherently interactive, allowing users to zoom, pan, and hover over data points. Let's create a more complex example that showcases Plotly's interactive features:

import streamlit as st
import plotly.graph_objects as go
import numpy as np

def create_interactive_plotly_chart(num_points, chart_type):
    x = np.linspace(0, 10, num_points)
    y = np.sin(x)
    
    if chart_type == 'Scatter':
        trace = go.Scatter(x=x, y=y, mode='markers')
    elif chart_type == 'Line':
        trace = go.Scatter(x=x, y=y, mode='lines')
    else:
        trace = go.Bar(x=x, y=y)
    
    fig = go.Figure(data=trace)
    fig.update_layout(title=f'{chart_type} Plot of Sine Wave',
                      xaxis_title='X-axis',
                      yaxis_title='Y-axis')
    
    return fig

st.title('Interactive Plotly in Streamlit')
num_points = st.slider('Number of Points', 10, 1000, 100)
chart_type = st.selectbox('Chart Type', ['Scatter', 'Line', 'Bar'])
st.plotly_chart(create_interactive_plotly_chart(num_points, chart_type))

This example allows users to adjust the number of data points and switch between different chart types. The resulting Plotly chart is fully interactive, providing a rich user experience.

Combining Matplotlib and Plotly

In some cases, you might want to use both Matplotlib and Plotly in the same Streamlit app. Here's an example of how you can do that:

import streamlit as st
import matplotlib.pyplot as plt
import plotly.graph_objects as go
import numpy as np

def create_matplotlib_chart():
    x = np.linspace(0, 10, 100)
    y = np.cos(x)
    
    fig, ax = plt.subplots()
    ax.plot(x, y)
    ax.set_title('Cosine Wave (Matplotlib)')
    ax.set_xlabel('X-axis')
    ax.set_ylabel('Y-axis')
    
    return fig

def create_plotly_chart():
    x = np.linspace(0, 10, 100)
    y = np.sin(x)
    
    fig = go.Figure(data=go.Scatter(x=x, y=y, mode='lines'))
    fig.update_layout(title='Sine Wave (Plotly)',
                      xaxis_title='X-axis',
                      yaxis_title='Y-axis')
    
    return fig

st.title('Matplotlib and Plotly in Streamlit')

col1, col2 = st.columns(2)

with col1:
    st.pyplot(create_matplotlib_chart())

with col2:
    st.plotly_chart(create_plotly_chart())

This example creates a two-column layout, displaying a Matplotlib chart in the left column and a Plotly chart in the right column.

Best Practices and Tips

1. Performance: For large datasets, consider using Plotly's go.Scattergl for improved rendering performance.

2. Customization: Explore the extensive customization options offered by both Matplotlib and Plotly to create visually appealing charts that match your app's design.

3. Responsive Design: Use Streamlit's layout options (e.g., st.columns()) to create responsive designs that work well on different screen sizes.

4. Caching: For computationally expensive chart generation, use Streamlit's @st.cache decorator to improve app performance.

5. Consistency: Try to maintain a consistent style across your visualizations, whether you're using Matplotlib, Plotly, or a combination of both.

By integrating Matplotlib and Plotly into your Streamlit apps, you can create powerful, interactive data visualizations that engage your users and effectively communicate your insights. Experiment with different chart types, customization options, and interactivity features to find the perfect visualization solution for your specific use case.