**R-squared**, often written R^{2}, is the proportion of the variance in the response variable that can be explained by the predictor variables in a linear regression model.

The value for R-squared can range from 0 to 1. A value of 0 indicates that the response variable cannot be explained by the predictor variable at all while a value of 1 indicates that the response variable can be perfectly explained without error by the predictor variables.

The **adjusted R-squared** is a modified version of R-squared that adjusts for the number of predictors in a regression model. It is calculated as:

**Adjusted R ^{2} = 1 – [(1-R^{2})*(n-1)/(n-k-1)]**

where:

**R**: The R^{2}^{2}of the model**n**: The number of observations**k**: The number of predictor variables

Since R^{2} always increases as you add more predictors to a model, adjusted R^{2} can serve as a metric that tells you how useful a model is, *adjusted for the number of predictors in a model*.

This tutorial shows two examples of how to calculate adjusted R^{2} for a regression model in Python.

**Related:** What is a Good R-squared Value?

**Example 1: Calculate Adjusted R-Squared with sklearn**

The following code shows how to fit a multiple linear regression model and calculate the adjusted R-squared of the model using sklearn:

from sklearn.linear_model import LinearRegression import pandas as pd #define URL where dataset is located url = "https://raw.githubusercontent.com/Statology/Python-Guides/main/mtcars.csv" #read in data data = pd.read_csv(url) #fit regression model model = LinearRegression() X, y = data[["mpg", "wt", "drat", "qsec"]], data.hp model.fit(X, y) #display adjusted R-squared 1 - (1-model.score(X, y))*(len(y)-1)/(len(y)-X.shape[1]-1) 0.7787005290062521

The adjusted R-squared of the model turns out to be **0.7787**.

**Example 2: Calculate Adjusted R-Squared with statsmodels**

The following code shows how to fit a multiple linear regression model and calculate the adjusted R-squared of the model using statsmodels:

import statsmodels.api as sm import pandas as pd #define URL where dataset is located url = "https://raw.githubusercontent.com/Statology/Python-Guides/main/mtcars.csv" #read in data data = pd.read_csv(url) #fit regression model X, y = data[["mpg", "wt", "drat", "qsec"]], data.hp X = sm.add_constant(X) model = sm.OLS(y, X).fit() #display adjusted R-squared print(model.rsquared_adj) 0.7787005290062521

The adjusted R-squared of the model turns out to be **0.7787**, which matches the result from the previous example.

**Additional Resources**

How to Perform Simple Linear Regression in Python

How to Perform Multiple Linear Regression in Python