Hovers

Hovers#

Some items when you hover your mouse over them show a hint. To control the properties of this tooltip, plotly offers a number of properties that usually start with hover.

Plotly user guide to work with it.

Hover template#

This is a variable that specifies how the information is displayed in the tooltip. For more information check section in the official documentation about hover templates.

Basic#

So in the following example there is a scatter with blue dots that have hovertemplate specified and a scatter with red dots that don’t have hovertemplate specified.

#| jupyter: python3

import numpy as np
import plotly.graph_objects as go

sample_size = 100

fig = go.Figure()
fig.add_trace(
    go.Scatter(
        x = np.random.rand(sample_size),
        y = np.random.rand(sample_size),
        mode = "markers",
        hovertemplate = "x=%{x}<br>y=%{y}",
        name = "I have hovertemplate",
        marker_size = 10
    )
)
fig.add_trace(
    go.Scatter(
        x = np.random.rand(sample_size),
        y = np.random.rand(sample_size),
        mode = "markers",
        marker={"color" : "red"},
        name = "No hovertemplate",
        marker_size = 10
    )
)

fig.update_layout(height = 700)

%{variable}#

You can display different parameters of elements on the plots, just using syntax {%variable}. And you can add some formatting, see here and here for dates.

#| jupyter: python3
import numpy as np
import plotly.graph_objects as go
from IPython.display import HTML

sample_size = 100

languages = ["R", "Python", "Java Script", "Matlab"]
users = [2, 5, 3, 2.5]
text = ["textA", "TextB", "TextC", "TextD"]

fig = go.Figure()
fig.add_trace(
    go.Pie(
        name = "",
        values = users,
        labels = languages,
        text = text,
        hovertemplate = "%{label}: <br>Popularity: %{percent} <br>%{text}<extra></extra>"
    )
)
fig.show()


fig = go.Figure()
fig.add_trace(
    go.Bar(
        x = languages,
        y = users,
        text = text,
        hovertemplate = "%{x} has %{y} users <extra></extra>"
    )
)
fig.show()

<extra>#

An additional block is added to the tooltip - by default, it is a semi-prominent part to the left of the main tooltip. Its content is resolved by the <extra> tag in hovertemplate. To get rid of it, the <extra> tag should be left empty.

So in the following example, I build the scatter with different cases with <extra>:

#| jupyter: python3
sample_size = 50

plot_params = [
    dict(name = "No hovertemplate"),
    dict(
        hovertemplate = "%{x} - %{y}",
        name = "No extra",
    ),
    dict(
        hovertemplate = "%{x} - %{y}<extra></extra>",
        name = "Empty extra",
    ),
    dict(
        hovertemplate = "%{x} - %{y}<extra>random hovertext %{hovertext}</extra>",
        name = "Content in extra",
        hovertext = [
            "".join(
                np.random.choice([i for i in "abdcefghijkilm"], 10)
            )
            for i in range(sample_size)
        ]
    )
]

fig = go.Figure()
for pp in plot_params:
    fig.add_trace(
        go.Scatter(
            x = np.random.rand(sample_size),
            y = np.random.rand(sample_size),
            mode = "markers",
            marker_size = 10,
            **pp
        )
    )

fig.update_layout(height = 700)

fig.show()
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