# Customize Linear Regression Fit Line Features

This post shows the customization you can apply to a linear regression fit line such as changing the color, transparency, and line width in a scatterplot built with seaborn.

## Libraries

First, we need to load a few libraries:

``````import pandas as pd
import matplotlib.pyplot as plt
import seaborn as sns``````

## Dataset

Since scatter plot are made for visualizing relationships between two numerical variables, we need a dataset that contains at least two numerical columns.

Here, we will use the `iris` dataset that we load directly from the gallery:

``````path = 'https://raw.githubusercontent.com/holtzy/The-Python-Graph-Gallery/master/static/data/iris.csv'
sepal_length sepal_width petal_length petal_width species
0 5.1 3.5 1.4 0.2 setosa
1 4.9 3.0 1.4 0.2 setosa
2 4.7 3.2 1.3 0.2 setosa
3 4.6 3.1 1.5 0.2 setosa
4 5.0 3.6 1.4 0.2 setosa

## Color and width

You can custom the appearance of the regression fit in a scatterplot built with seaborn thanks to the `line_kws` argument.

This argument accepts a dictionary of argument names and their values. These values will be exclusively used to style the line. For example, `line_kws={"color" : "red", "linewidth" : 1.5}` will render the line red and with a width of 1.5.

``````fig, ax = plt.subplots(figsize=(8, 6))
sns.regplot(
x=df["sepal_length"],
y=df["sepal_width"],
line_kws={"color": "red", "linewidth": 1.5},
ax=ax
)
plt.show()``````

## Opacity

You can also custom the opacity of the line with the `alpha` value:

``````fig, ax = plt.subplots(figsize=(8, 6))
sns.regplot(
x=df["sepal_length"],
y=df["sepal_width"],
line_kws={
"color": "r",
"alpha": 0.4
},
ax=ax
)
plt.show()``````

## Line width and style

You can also custom the line width and style with the `linewidth` and `linestyle` values:

``````fig, ax = plt.subplots(figsize=(8, 6))
sns.regplot(
x=df["sepal_length"],
y=df["sepal_width"],
line_kws={
"color": "darkred",
"alpha": 0.4,
"lw": 5,
"ls": "--"
},
ax=ax
)
plt.show()``````

## Going further

This post explains how to customize the appearance of a regression fit in a scatter plot with seaborn.

You might be interested in more advanced examples on:

## Contact & Edit

👋 This document is a work by Yan Holtz. You can contribute on github, send me a feedback on twitter or subscribe to the newsletter to know when new examples are published! 🔥