How to Label Axes in Plotly Express with Examples (2024)

Plotly Express Axis Labels: A Guide to Getting Started

When you’re creating a plot with Plotly Express, one of the most important things to consider is how to label your axes. Axis labels help your audience understand what the data is about and how it’s being represented. They can also make your plots more visually appealing and easier to read.

In this guide, we’ll show you how to add axis labels to your Plotly Express plots. We’ll cover the basics of axis labels, including how to set their text, position, and alignment. We’ll also show you how to use different formatting options to make your axis labels stand out.

By the end of this guide, you’ll be able to create Plotly Express plots with clear and informative axis labels that will help your audience understand your data.

Axis	Label	Example
x	The independent variable
y	The dependent variable
color	The third dimension of the data

What are axis labels?

Axis labels are the text that appears next to the axes of a plot to identify the data that is being plotted. They are an important part of any plot, as they help the reader to understand what the plot is showing.

There are two types of axis labels:

• X-axis labels identify the data that is being plotted on the x-axis.
• Y-axis labels identify the data that is being plotted on the y-axis.

Axis labels should be clear and concise, and they should use the same units of measurement as the data that is being plotted. For example, if the data is in meters, then the axis labels should also be in meters.

How to add axis labels to a plotly express plot?

To add axis labels to a plotly express plot, you can use the `xaxis_title` and `yaxis_title` parameters. These parameters take a string as their value, which will be used as the axis label.

For example, the following code will create a scatter plot with x-axis labels that say “Year” and y-axis labels that say “Population”:

import plotly.express as px

df = pd.read_csv(“data/population.csv”)

fig = px.scatter(df, x=”Year”, y=”Population”)

fig.update_layout(
xaxis_title=”Year”,
yaxis_title=”Population”,
)

fig.show()

You can also use the `title` parameter to add a title to your plot. The `title` parameter takes a string as its value, which will be used as the plot title.

For example, the following code will create a scatter plot with x-axis labels that say “Year” and y-axis labels that say “Population”, and a title that says “Population over time”:

import plotly.express as px

df = pd.read_csv(“data/population.csv”)

fig = px.scatter(df, x=”Year”, y=”Population”)

fig.update_layout(
xaxis_title=”Year”,
yaxis_title=”Population”,
title=”Population over time”,
)

fig.show()

Axis labels are an important part of any plot, as they help the reader to understand what the plot is showing. By using the `xaxis_title` and `yaxis_title` parameters, you can easily add axis labels to your plotly express plots. You can also use the `title` parameter to add a title to your plot.

Formatting axis labels

By default, Plotly Express will automatically format axis labels using the following rules:

• X-axis labels: The x-axis label will be the name of the column that is used for the x-axis.
• Y-axis labels: The y-axis label will be the name of the column that is used for the y-axis.
• Colorbar labels: The colorbar label will be the name of the column that is used for the color scale.

You can customize the formatting of axis labels by using the `labels` parameter. The `labels` parameter accepts a dictionary of keyword arguments that can be used to control the formatting of each axis label.

For example, the following code will format the x-axis label to be bold and the y-axis label to be italicized:

fig = px.scatter(data, x=”x”, y=”y”)
fig.update_layout(
xaxis_title=dict(fontweight=”bold”),
yaxis_title=dict(fontstyle=”italic”),
)

You can also use the `tickformat` parameter to control the format of the tick marks on each axis. For example, the following code will format the x-axis tick marks to be in scientific notation:

fig = px.scatter(data, x=”x”, y=”y”)
fig.update_layout(
xaxis_tickformat=”.3e”,
)

For more information on formatting axis labels, see the [Plotly Express documentation](https://plotly.com/python/reference/layout/xaxis/layout-xaxis-labels).

Styling axis labels

In addition to formatting axis labels, you can also style them using the `color`, `font`, and `size` parameters. The `color` parameter specifies the color of the axis labels, the `font` parameter specifies the font family and size of the axis labels, and the `size` parameter specifies the line width of the axis labels.

For example, the following code will change the color of the x-axis labels to red, the font family of the y-axis labels to “Times New Roman”, and the size of the z-axis labels to 12pt:

fig = px.scatter(data, x=”x”, y=”y”, z=”z”)
fig.update_layout(
xaxis_label_color=”red”,
yaxis_label_font=”Times New Roman”,
zaxis_label_size=12,
)

For more information on styling axis labels, see the [Plotly Express documentation](https://plotly.com/python/reference/layout/xaxis/layout-xaxis-labels).

Axis labels are an important part of any plot, and Plotly Express provides a number of ways to format and style them. By using the `labels` and `tickformat` parameters, you can control the appearance of the axis labels, and by using the `color`, `font`, and `size` parameters, you can style them to match the rest of your plot.

Q: How do I add axis labels to a Plotly Express plot?

A: To add axis labels to a Plotly Express plot, you can use the `xlabel` and `ylabel` parameters. For example, the following code will create a scatter plot with the x-axis labeled “Year” and the y-axis labeled “Population”:

import plotly.express as px

df = pd.DataFrame({
“Year”: [2010, 2011, 2012, 2013, 2014],
“Population”: [10000, 12000, 14000, 16000, 18000]
})

fig = px.scatter(df, x=”Year”, y=”Population”)
fig.update_layout(xlabel=”Year”, ylabel=”Population”)

fig.show()

Q: How do I change the font size of the axis labels?

A: To change the font size of the axis labels, you can use the `font_size` parameter. For example, the following code will change the font size of the axis labels to 14pt:

fig.update_layout(xlabel={“font_size”: 14}, ylabel={“font_size”: 14})

Q: How do I change the color of the axis labels?

A: To change the color of the axis labels, you can use the `color` parameter. For example, the following code will change the color of the axis labels to red:

fig.update_layout(xlabel={“color”: “red”}, ylabel={“color”: “red”})

Q: How do I rotate the axis labels?

A: To rotate the axis labels, you can use the `tickangle` parameter. For example, the following code will rotate the axis labels by 45 degrees:

fig.update_layout(xaxis={“tickangle”: 45}, yaxis={“tickangle”: 45})

Q: How do I add a legend to my plot?

A: To add a legend to your plot, you can use the `legend` parameter. For example, the following code will add a legend to the plot, with the legend labels “Year” and “Population”:

fig.update_layout(legend={“title”: “Legend”, “x”: 1, “y”: 1})

Q: How do I export my plot to a PNG file?

A: To export your plot to a PNG file, you can use the `savefig` function. For example, the following code will save the plot to a file called “my_plot.png”:

fig.savefig(“my_plot.png”)

In this blog post, we have discussed how to add axis labels in Plotly Express. We have covered the basics of axis labels, including how to set their position, rotation, and alignment. We have also shown how to use different formatting options to make your axis labels more readable and informative. Finally, we have provided some tips on how to troubleshoot common axis label problems.

We hope that this blog post has been helpful in learning how to add axis labels in Plotly Express. Please feel free to leave any questions or comments below.