Logistic Regression

Find the probability of data samples belonging to a specific class with one of the most popular classification algorithms.

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Key Concepts

Review core concepts you need to learn to master this subject

Scikit-Learn Logistic Regression Implementation

Logistic Regression sigmoid function

Classification Threshold definition

Logistic Regression interpretability

Log-Odds calculation

Logistic Regression Classifier

Logistic Regression prediction

Logistic Regression cost function

Scikit-Learn Logistic Regression Implementation

Scikit-Learn has a Logistic Regression implementation that fits a model to a set of training data and can classify new or test data points into their respective classes. All important parameters can be specified, as the norm used in penalizations and the solver used in optimization.

Logistic Regression

Lesson 1 of 1

1
Introduction
When an email lands in your inbox, how does your email service know whether it’s real or spam? This evaluation is made billions of times per day, and one possible method is logistic regression. _…
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2
Linear Regression Approach
With the data from Codecademy University, we want to predict whether each student will pass their final exam. Recall that in linear regression, we fit a line of the following form to the data: y =…
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3
Logistic Regression
We saw that predicted outcomes from a linear regression model range from negative to positive infinity. These predictions don’t really make sense for a classification problem. Step in _**logistic r…
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4
Log-Odds
So far, we’ve learned that the equation for a logistic regression model looks like this: ln(\frac{p}{1-p}) = b_{0} + b_{1}x_{1} + b_{2}x_{2} +\cdots + b_{n}x_{n} Note that we’ve replaced y wit…
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5
Sigmoid Function
Let’s return to the logistic regression equation and demonstrate how this works by fitting a model in sklearn. The equation is: ln(\frac{p}{1-p}) = b_{0} + b_{1}x_{1} + b_{2}x_{2} +\cdots + b_{n}x…
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6
Fitting a model in sklearn
Now that we’ve learned a little bit about how logistic regression works, let’s fit a model using [sklearn](http://scikit-learn.org/stable/modules/generated/sklearn.linear_model.LogisticRegression.h…
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7
Predictions in sklearn
Using a trained model, we can predict whether new datapoints belong to the positive class (the group labeled as 1) using the .predict() method. The input is a matrix of features and the output is a…
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8
Classification Thresholding
As we’ve seen, logistic regression is used to predict the probability of group membership. Once we have this probability, we need to make a decision about what class a datapoint belongs to. This is…
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9
Confusion matrix
When we fit a machine learning model, we need some way to evaluate it. Often, we do this by splitting our data into training and test datasets. We use the training data to fit the model; then we us…
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10
Accuracy, Recall, Precision, F1 Score
Once we have a confusion matrix, there are a few different statistics we can use to summarize the four values in the matrix. These include accuracy, precision, recall, and F1 score. We won’t go int…
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11
Review
Congratulations! You just learned how a logistic regression model works and how to fit one to a dataset. Here are some of the things you learned: * Logistic regression is used to perform binary cla…
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