How to create Ternary Overlay using Plotly?

Ternary plots are a useful way to display compositional data where three variables add up to a constant value. Plotly is a powerful plotting library that can be used to create interactive ternary plots with ease. In this tutorial, we will explore how to create a Ternary Overlay using Plotly.

To create a Ternary Overlay using Plotly, we use the scatterternary trace type. This trace type creates a scatter plot on a ternary diagram, where the components A, B, and C represent the vertices of an equilateral triangle. The position of each point within the triangle represents the proportion of each component in the data point.

Basic Ternary Plot

Here's an example of creating a basic ternary plot with three data points ?

import plotly.graph_objects as go

trace = go.Scatterternary(
    a=[0.2, 0.4, 0.1],
    b=[0.4, 0.1, 0.3], 
    c=[0.4, 0.5, 0.6],
    mode='markers',
    marker=dict(
        symbol='circle',
        color='blue',
        size=10
    )
)

layout = go.Layout(
    ternary=dict(
        sum=1,
        aaxis=dict(title='Component A'),
        baxis=dict(title='Component B'),
        caxis=dict(title='Component C')
    )
)

fig = go.Figure(data=[trace], layout=layout)
fig.show()

In this example, we create a scatter plot with three points on a ternary diagram. The a, b, and c arrays represent the proportion of each component in each data point. The sum=1 parameter specifies that the three components should sum to 1.

Customized Ternary Plot with Labels

This example creates a more customized ternary plot with colored markers and text labels ?

import plotly.graph_objects as go

fig = go.Figure(go.Scatterternary({
    'mode': 'markers+text',
    'a': [0.1, 0.3, 0.5, 0.7, 0.9],
    'b': [0.2, 0.4, 0.6, 0.8, 0.1], 
    'c': [0.7, 0.3, 0.1, 0.4, 0.6],
    'marker': {
        'symbol': 'circle',
        'color': ['red', 'green', 'blue', 'yellow', 'purple'],
        'size': 12,
        'line': {'width': 2, 'color': 'white'}
    },
    'text': ['A', 'B', 'C', 'D', 'E'],
    'textposition': 'middle center'
}))

fig.update_layout({
    'ternary': {
        'sum': 1,
        'aaxis': {'title': 'Variable 1'},
        'baxis': {'title': 'Variable 2'}, 
        'caxis': {'title': 'Variable 3'}
    },
    'title': 'Ternary Plot with Labeled Points',
    'height': 500
})

fig.show()

This example creates a scatter plot with 5 points labeled A through E. Each point has a different color and displays text labels. The mode='markers+text' parameter enables both markers and text display.

Key Parameters

Conclusion

Ternary plots are excellent for visualizing compositional data in fields like chemistry, geology, and ecology. Plotly's scatterternary provides an easy way to create interactive ternary overlays with customizable markers, colors, and labels.