# dataset

- dependent variable: profit
- y = b0 + b1 * x1 + b2 * x2 + b3 * x3 + ???
- x1: R&D , x2: Admin , x3: marketing
- State 是 categorical variable，要轉換為 dummy variable
- y = b0 + b1 * x1 + b2 * x2 + b3 * x3 + b4 + D1 
- 使用 New York cloumn 即可， California column 的資訊可以不放入

![image](https://github.com/kevingo/ml-az/raw/834e6282a8b17b5e43dbea7f13b2954f77a49449/screenshots/dummyvariable.png)

# Linear Regression 的前提
- Linearity 線性
- Independence of the errors
- Homoscedasticity 同質性
- Normality of the error distribution 錯誤呈現常態分配
- 預測變量之中沒有多重共線性

# Dummy Variable Trap
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