*Regressions*

*Regressions*

Updated at 2017-11-13 14:39

**Regression analysis** is a statistical process for estimating the relationships among variables.

In regression machine learning problems, the desired output is a continuous number e.g. age of a person.

**Simple Linear Regression**: a linear predictor function with one input variable e.g.`(y = x^2)`

.**Multiple Linear Regression**: a linear predictor function with more than one input variable.**Ordinal Regression**: model output is an ordinal variables thus have an order but unknown distance between themselves e.g. "good", "ok", "poor".**Nonlinear Regression**: the predictor function is nonlinear such as exponentiation^2. There may be multiple local minima to optimize.**General Linear Model**: a matrix formula (`y = xb + u`

) which has input matrix`x`

, output matrix`y`

, model coefficiency matrix (`b`

) and error matrix`u`

.`b`

works like neural network weights and`u`

like bias, finding the right matrix values for those will allow creating predictions.**Generalized Linear Model (GLM)**: allows for outputs that have error distribution models other than a normal distribution by allowing the linear model to be related to the response variable via a link function.

# Logistic Regressions

**Logistic Regression**predictions are categorical.**Binary Logistic Regression**predictions are either 0 or 1.**Multinomial Logistic Regression**predictions can be more than 2 possible discrete outcomes.**Ordered Logistic Regression**predictions are ordinal e.g. "poor", "fair" and "good".

# Sources

- sklearn - ML General Concepts
- The Master Algorithm, Pedro Domingos
- Wikipedia