Machine Learning — Logistic Regression with Python. A practical introduction to Logistic Regression for classification and predictions in Python

Logistic Regression is an algorithm that can be used for regression as well as classification tasks but it is widely used for classification tasks. The response variable that is binary belongs either to one of the classes. It is used to predict categorical variables with the help of dependent variables. Consider there are two classes and a new data point is to be checked which class it would belong to. Then algorithms compute probability values that range from 0 and 1. For example, whether it will rain today or not. In logistic regression weighted sum of input is passed through the sigmoid activation function and the curve which is obtained is called the sigmoid curve.

Logistic regression uses an equation as the representation, very much like linear regression. Input values (x) are combined linearly using weights or coefficient values (referred to as the Greek capital letter Beta) to predict an output value (y). A key difference from linear regression is that the output value being modeled is a binary value (0 or 1) rather than a numeric value.

Below is an example logistic regression equation:

**y = e^(b0 + b1 x) / (1 + e^(b0 + b1x))**

Where y is the predicted output, b0 is the bias or intercept term and b1 is the coefficient for the single input value (x). Each column in your input data has an associated b coefficient (a constant real value) that must be learned from your training data. The actual representation of the model that you would store in memory or in a file is the coefficients in the equation (the beta value or b’s).

using a given set of independent features whereas*Linear regression is used for predicting the continuous dependent variable*.*Logistic Regression is used to predict the categorical*- Linear regression is used to
whereas logistic regression is used to*solve regression problems*.*solve classification problems* - In Linear regression, the approach is to find the best fit line to predict the output whereas in the Logistic regression approach is to try for S curved graphs that classify between the two classes that are 0 and 1.
- The method for accuracy in linear regression is the
whereas for logistic regression it is*least square estimation*.*maximum likelihood estimation* - In Linear regression,
like price & age, whereas in Logistic regression*the output should be continuous*like either Yes / No or 0/1.*the output must be categorical* - There should be a
between the dependent and independent features in the case of Linear regression whereas it is*linear relationship*.*not in the case of Logistic regression* - There can be collinearity between independent features in the case of linear regression but it is not in the case of logistic regression.

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