Use Pandas index in Plotly Express

Question

Plotly Express allows me to easily plot a pandas dataframe, as explained in their examples. Rather than using a named column for x and a named column for y, I would like to use the dataframe's index for x and a named column for y.

Example using named columns

import plotly.express as px
iris = px.data.iris()
fig = px.scatter(iris, x="sepal_width", y="sepal_length")
fig.show()

What i want (bogus example)

import plotly.express as px
iris = px.data.iris()
fig = px.scatter(iris, x="index", y="sepal_length")
fig.show()

This obviously throws:

ValueError: Value of 'x' is not the name of a column in 'data_frame'. Expected one of ['sepal_length', 'sepal_width', 'petal_length', 'petal_width', 'species', 'species_id'] but received: index

Ugly fix

import plotly.express as px
iris = px.data.iris().reset_index()
fig = px.scatter(iris, x="index", y="sepal_length")
fig.show()

@nicolaskruchten With my own data (pandaframes resuting from some web scraping) I found the "ugly fix" to be the way to go, too. Hence, I'd suggest making your answer (together with a link to some official documentation (I found nothing on that case)) the official answer. — StefanQ
– StefanQ, Commented Aug 25, 2019 at 10:21
@StefanQ I'm hoping to actually add support for this kind of thing in the next few weeks :) — nicolaskruchten
– nicolaskruchten, Commented Aug 25, 2019 at 18:32
Feel free to post your above remarks as answer and I will mark it accordingly. Makes it easy for you to keep the community up to date! — Laurens Koppenol
– Laurens Koppenol, Commented Aug 26, 2019 at 10:42

syltruong · Accepted Answer · 2020-02-21 06:13:14Z

62

Reference: https://plot.ly/python/px-arguments/#using-the-index-of-a-dataframe

You can pass the index as reference explicitly.

So in your case, this would be:

import plotly.express as px
iris = px.data.iris()
fig = px.scatter(iris, x=iris.index, y="sepal_length")
fig.show()

--

BONUS QUESTION: what if iris has a pd.MultiIndex?

Use pd.MultiIndex.get_level_values.

import plotly.express as px

# dummy example for multiindex
iris = px.data.iris().set_index(['species', 'species_id', iris.index])

fig = px.scatter(
   iris, 
   x=iris.index.get_level_values(2), 
   y="sepal_length"
)

fig.show()

answered Feb 21, 2020 at 6:13

syltruong

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4 Comments

Eulenfuchswiesel Over a year ago

Does this also work with a DatetimeIndex? I am having some difficulties with this issue at the moment

soungalo Over a year ago

Note that this geature has been added somewhere after plotly version 4.1 (had to update for this to work).

Abhishek Sourabh Over a year ago

This results in the x-axis label being "x". Is there a way to assign so that x-axis uses the label of the index being used?

syltruong Over a year ago

The example in the comment would use the name of the index as x-axis label on the plot. You can try this behaviour with: ``` import plotly.express as px iris = px.data.iris() iris.index.rename("my_custom_index", inplace=True) fig = px.scatter(iris, x=iris.index, y="sepal_length") fig.show() ```

PassingThrough · Accepted Answer · 2019-12-27 00:44:49Z

6

You can simply leave it blank, like so:

import plotly.express as px
iris = px.data.iris()
fig = px.scatter(iris, y="sepal_length")
fig.show()

answered Dec 27, 2019 at 0:44

PassingThrough

1251 silver badge2 bronze badges

1 Comment

Christian Aichinger Over a year ago

This does not use the index for the x axis! It uses range(iris.index.size) as X axis.

vestland · Accepted Answer · 2020-02-21 06:16:29Z

-2

You can only pass the column name at x & y parameters of px.scatter(). Seems there is no column named "index" in the iris dataset.

edited Feb 21, 2020 at 6:16

vestland

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answered Jul 24, 2019 at 8:33

user11818600

1 Comment

Laurens Koppenol Over a year ago

Thanks for your reply. This is what I wanted to point out with my bogus example.

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