# What is cost function for logistic regression?

## What is cost function for logistic regression?

The cost function used in Logistic Regression is Log Loss.

**What is the cost function of the logistic regression Mcq?**

The cost function of logistic regression is derived from taking the log of the maximum likelihood function and applying negative to log loss function in order to use gradient descent for optimization purposes. This is why the cross-entropy loss function is also called a log loss function.

**Why is the cost function of logistic regression negative?**

When we think about the loss function we want to have something that is bounded by 0 from below and is unbounded for positive values. Our goal is to minimize the cost function. Hence, we take the negative of the log likelihood and use it as our cost function.

### What is the function of logistic regression?

Like all regression analyses, logistic regression is a predictive analysis. Logistic regression is used to describe data and to explain the relationship between one dependent binary variable and one or more nominal, ordinal, interval or ratio-level independent variables.

**Why we use sigmoid function in logistic regression?**

What is the Sigmoid Function? In order to map predicted values to probabilities, we use the Sigmoid function. The function maps any real value into another value between 0 and 1. In machine learning, we use sigmoid to map predictions to probabilities.

**What loss function is used for logistic regression?**

Log Loss

Log Loss is the loss function for logistic regression. Logistic regression is widely used by many practitioners.

#### Why cost function which has been used for linear regression can be used for logistic regression?

The method most commonly used for logistic regression is gradient descent. Gradient descent requires convex cost functions. Mean Squared Error, commonly used for linear regression models, isn’t convex for logistic regression. This is because the logistic function isn’t always convex.

**Is the cost function for logistic regression always non negative?**

The cost function J(θ) for logistic regression trained with examples is always greater than or equal to zero. The cost for any example x(i) is always ≥ 0 since it is the negative log of a quantity less than one.

**What is the cost function for linear regression?**

The cost function of a linear regression is root mean squared error or mean squared error. They are both the same; just we square it so that we don’t get negative values.

## What is difference between logistic function and sigmoid function?

The logistic function in linear regression is a type of sigmoid, a class of functions with the same specific properties. Sigmoid is a mathematical function that takes any real number and maps it to a probability between 1 and 0.

**Is cost function same as loss function?**

Difference between Loss and Cost Function We usually consider both terms as synonyms and think that they can be used interchangeably. But, the Loss function is associated with every training example, and the cost function is the average value of the loss function over all the training samples.

**How do you find the cost function in logistic regression?**

Logistic regression cost function For logistic regression, the C o s t function is defined as: C o s t (h θ (x), y) = { − log (h θ (x)) if y = 1 − log

### Why do we need a convex function for logistic regression?

That’s why we still need a neat convexfunction as we did for linear regression: a bowl-shaped function that eases the gradient descent function’s work to converge to the optimal minimum point. A better cost function for logistic regression Let me go back for a minute to the cost function we used in linear regression:

**What is the C O S T function in logistic regression?**

For logistic regression, the C o s t function is defined as: The i indexes have been removed for clarity. In words this is the cost the algorithm pays if it predicts a value h θ ( x) while the actual cost label turns out to be y.

**How to minimize the cost function in a linear regression?**

The minimization will be performed by a gradient descent algorithm, whose task is to parse the cost function output until it finds the lowest minimum point. The cost function used in linear regression won’t work here