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Ternary Overlay in Python

How to make a scatter plot overlaid on ternary contour in Python with Plotly.

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Alternatively, download this entire tutorial as a Jupyter notebook and import it into your Workspace.
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New to Plotly?

Plotly is a free and open-source graphing library for Python. We recommend you read our Getting Started guide for the latest installation or upgrade instructions, then move on to our Plotly Fundamentals tutorials or dive straight in to some Basic Charts tutorials.

Load and Process Data Files

In [1]:
import json
import pandas as pd

contour_raw_data = pd.read_json('')
scatter_raw_data = pd.read_json('')

scatter_data =  scatter_raw_data['Data']

def clean_data(data_in):
    Cleans data in a format which can be conveniently
    used for drawing traces. Takes a dictionary as the
    input, and returns a list in the following format:

    input = {'key': ['a b c']}
    output = [key, [a, b, c]]
    key = list(data_in.keys())[0]
    data_out = [key]
    for i in data_in[key]:
        data_out.append(list(map(float, i.split(' '))))

    return data_out

print(clean_data({'L1': ['.03 0.5 0.47','0.4 0.5 0.1']}))
['L1', [0.03, 0.5, 0.47], [0.4, 0.5, 0.1]]

Create Ternary Scatter Plot:

In [2]:
import plotly.graph_objects as go

a_list = []
b_list = []
c_list = []
text = []

for raw_data in scatter_data:
    data = clean_data(raw_data)

fig = go.Figure(go.Scatterternary(
  marker={'symbol': 100,
          'color': 'green',
          'size': 10},

    'title': 'Ternary Scatter Plot',
        'aaxis':{'title': 'X', 'min': 0.01, 'linewidth':2, 'ticks':'outside' },
        'baxis':{'title': 'W', 'min': 0.01, 'linewidth':2, 'ticks':'outside' },
        'caxis':{'title': 'S', 'min': 0.01, 'linewidth':2, 'ticks':'outside' }
    'showlegend': False

Create Ternary Contour Plot:

In [3]:
import plotly.graph_objects as go

contour_dict = contour_raw_data['Data']

# Defining a colormap:
colors = ['#8dd3c7','#ffffb3','#bebada',
colors_iterator = iter(colors)

fig = go.Figure()

for raw_data in contour_dict:
    data = clean_data(raw_data)

    a = [inner_data[0] for inner_data in data[1:]]
    a.append(data[1][0]) # Closing the loop

    b = [inner_data[1] for inner_data in data[1:]]
    b.append(data[1][1]) # Closing the loop

    c = [inner_data[2] for inner_data in data[1:]]
    c.append(data[1][2]) # Closing the loop

        text = data[0],
        a=a, b=b, c=c, mode='lines',
        line=dict(color='#444', shape='spline'),
        fillcolor = colors_iterator.__next__()

fig.update_layout(title = 'Ternary Contour Plot')
In [ ]:

What About Dash?

Dash is an open-source framework for building analytical applications, with no Javascript required, and it is tightly integrated with the Plotly graphing library.

Learn about how to install Dash at

Everywhere in this page that you see, you can display the same figure in a Dash application by passing it to the figure argument of the Graph component from the built-in dash_core_components package like this:

import plotly.graph_objects as go # or as px
fig = go.Figure() # or any Plotly Express function e.g.
# fig.add_trace( ... )
# fig.update_layout( ... )

import dash
import dash_core_components as dcc
import dash_html_components as html

app = dash.Dash()
app.layout = html.Div([

app.run_server(debug=True, use_reloader=False)  # Turn off reloader if inside Jupyter