Plotly · Function

px.line_ternary

Creates an interactive ternary line plot from tabular data. Rows become ternary points, while coordinate, grouping, color, and other Plotly Express arguments control the generated figure.

How it works

px.line_ternary creates a complete interactive ternary line figure from tabular data. Each row contributes a point positioned by the a, b, and c values; optional grouping and styling arguments determine which points connect and how the resulting traces appear.

Syntax

plotly.express.line_ternary(data_frame=None, a=None, b=None, c=None, color=None, line_dash=None, hover_name=None, hover_data=None, custom_data=None, text=None, symbol=None, animation_frame=None, animation_group=None, category_orders=None, labels=None, color_discrete_sequence=None, color_discrete_map=None, line_dash_sequence=None, line_dash_map=None, symbol_sequence=None, symbol_map=None, markers=None, log_a=False, log_b=False, log_c=False, range_a=None, range_b=None, range_c=None, title=None, template=None, width=None, height=None)

Parameters

Name	Type	Description
`data_frame`	`DataFrame or array-like`	Data frame containing the columns used by the chart and its encodings.
`a`	`str or array-like`	Column or array specifying the first ternary coordinate.
`b`	`str or array-like`	Column or array specifying the second ternary coordinate.
`c`	`str or array-like`	Column or array specifying the third ternary coordinate.
`color, line_group, and other keyword arguments`	`optional`	Optional grouping/color encoding and additional Plotly Express styling arguments.

Returns

A plotly.graph_objects.Figure containing the generated interactive ternary line chart.

Key points

The function belongs to Plotly Express, the high-level API intended for quickly generating complete figures.
Its primary inputs include a data frame, three ternary coordinate mappings, and optional visual-encoding arguments.
Input rows become plotted ternary points, allowing a data frame to describe the chart’s observations.

Common mistakes

The function represents every input row as a ternary point; use line_group when rows should be connected into separate trajectories.

Example: Line ternary chart

import plotly.express as px

df = px.data.iris()
fig = px.line_ternary(
    df,
    a="sepal_width",
    b="sepal_length",
    c="petal_length",
    color="species",
    line_group="species",
    markers=True,
)
fig.show()

Creates an interactive ternary line chart from the Iris data, using three columns as ternary coordinates and grouping/coloring lines by species.

When to use it

Composition trajectories

Plot compositional measurements whose three components define a ternary position over ordered observations.

Grouped ternary paths

Compare multiple entities by assigning a grouping column and optionally a color encoding.

Rapid data-frame visualization

Build exploratory interactive charts directly from a pandas data frame.

Interview questions

QWhat does px.line_ternary create?

px.line_ternary is Plotly Express’s high-level constructor for ternary line plots. It returns a complete interactive figure rather than only a trace.

Follow-up: How would you create a ternary line without Plotly Express? Use a graph_objects Scatterternary trace and assign its a, b, and c coordinates.

QWhat do a, b, and c represent?

The a, b, and c arguments identify the three data columns used for ternary coordinates. The function consumes these columns for every row in the supplied data frame.

Follow-up: What should be checked when coordinates appear incorrect? Verify that the selected columns contain the intended numeric components and that the ternary layout’s normalization assumptions match the data.

QHow is the resulting figure typically used?

The function is designed for a data-frame-oriented workflow: pass the data frame first, then map columns and optional visual encodings such as color or line grouping. The result can be displayed with fig.show().

Follow-up: How can the chart be customized after construction? Modify the returned Figure with Plotly Figure methods, including layout and trace updates.

plotly.express.scatter_ternary
plotly.graph_objects.Scatterternary
plotly.express.line

Source: plotly.express : high-level interface for data visualization. Checked 2026-10-15.