### sigmoid function

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A function that maps logistic or multinomial regression output (log odds) to probabilities, returning a value between 0 and 1. The sigmoid function has the following formula:

![Sigmoid function](https://i.imgur.com/Smha9eb.png)

where $\sigma$ in logistic regression problems is simply:

![sigma in a logistica regression is](https://i.imgur.com/D2oA7ed.png)

In other words, the sigmoid function converts

into a probability between 0 and 1.

In some neural networks, the sigmoid function acts as the activation function.