linear bai 1.Rmd

---
title: "linear bai 1"
output: html_document
date: "2023-10-07"
---

```{r setup, include=FALSE}
knitr::opts_chunk$set(echo = TRUE)
```

## R Markdown

This is an R Markdown document. Markdown is a simple formatting syntax for authoring HTML, PDF, and MS Word documents. For more details on using R Markdown see <http://rmarkdown.rstudio.com>.

When you click the **Knit** button a document will be generated that includes both content as well as the output of any embedded R code chunks within the document. You can embed an R code chunk like this:

#tai cac packages
```
install.packages("ggplot2")
install.packages("dplyr")
```

#tai cac libraries
```
library(ggplot2)
library(dplyr)
library(tidyr)
library(haven)
```
#doc file regression
```
df <- read_dta("Regression.dta")
View(df)
```
#phan tich tuong quan
```
cov(df$c38, df$wage, method ="pearson")
cor(df$c38, df$wage, method ="pearson")
```

#linear regression 1 sample
```
reg1 <- lm(wage ~ c38, data = df)
summary(reg1)
plot(df$c38, df$wage, xlab = "c38", ylab = "wage", col = "blue")
abline(reg1, col = "Red")
```
#phan tich hoi quy cho tung mau
```
dt = sort(sample(nrow(df),nrow(df)*.5))
df1 <- df[dt,]
df2 <- df[-dt,]

dim(df1)
dim(df2)

reg2 <- lm(df1$wage ~ df1$c38)
reg3 <- lm(df2$wage ~ df2$c38)
```
#danh gia cac tham so cho tung mo hinh hoi quy mau
```
summary(reg2)
summary(reg3)

plot(df$c38, df$wage, xlab = "c38", ylab = "wage", col = "blue")
abline(reg1, col = "Red")
abline(reg2, col = "Yellow")
abline(reg3, col = "Green")
```