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Mastering Predictive Analytics with R by Rui Miguel Forte

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Introduction to logistic regression

In logistic regression, input features are linearly scaled just as with linear regression; however, the result is then fed as an input to the logistic function. This function provides a nonlinear transformation on its input and ensures that the range of the output, which is interpreted as the probability of the input belonging to class 1, lies in the interval [0,1]. The form of the logistic function is as follows:

Introduction to logistic regression

Here is a plot of the logistic function:

Introduction to logistic regression

When x = 0, the logistic function takes the value 0.5. As

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