Plotly and the Plotly Figure

Introduction to Data Visualization with Plotly in Python

Alex Scriven

Data Scientist

What is Plotly?

A JavaScript graphing library
- Don't worry - no need to know JavaScript!
Plotly has a Python wrapper

Plotly logo

Why Plotly?

Plotly has a number of unique advantages:

Fast and easy to use
Low code/low effort options using plotly.express
(If desired) Extremely customizable
Built-in interactivity

Creating Plotly Figures

Plotly graphs can be created:

With plotly.express for quick plots (px)
With plotly.graph_objects (go) for more customization

📈 We will spend most of our time on px

The importance of documentation

Save the links to key documentation!

Interactive documentation
Detailed reference page for specific plots

For Scatter plots:

plotly.express page with examples
Technical reference for the underlying object

Creating our Figure

A basic plotly figure:

import plotly.express as px

days = ["Monday", "Tuesday", "Wednesday", "Thursday", 
        "Friday", "Saturday", "Sunday"]       
temperatures = [28, 27, 25, 31, 32, 35, 36]

fig = px.bar(
    x=days, 
    y=temperatures,
    title="Temperatures of the week")

fig.show()

Our Figure revealed

Bar chart of weekly temperatures

The Plotly Figure

Plotly Figure components:

layout: Dictionary controlling style of the figure
- One layout per figure
data: List of dictionaries setting graph type and data itself
- Data + type = a trace. There are over 40 types!
- Can have multiple traces per graph
frames: For animated plots (beyond this course)

Inside a Plotly Figure

print(fig)

Figure({'data': [{'type': 'bar',
              'x': array(['Monday', 'Tuesday', 'Wednesday', 'Thursday', 'Friday'
              , 'Saturday','Sunday'], dtype=object),
              'y': {'bdata': 'HBsZHyAjJA==....'}],
    'layout': {'title': {'text': 'Temperatures of the week'}}})

Plotly's instant interactivity

Hover over data points
Extra interactive buttons

Hover options

Let's practice!

Introduction to Data Visualization with Plotly in Python