###LESSON 3 EXERCISE OF CHI-SQURE & FISHER EXACT TEST (12/4/2021)

library(haven)
setwd("S:/_STAFF/Gulser/R NOTES/lesson_2_stata")
dataset<-read_dta('all215187.dta')
dataset

attach(dataset)
dataset

table(fumo)
table(infarto)
summary(dataset)

fumo.infarto<-table(fumo, infarto)
fumo.infarto

###COUNTING
margin.table(fumo.infarto, 1)
margin.table(fumo.infarto, 2)

###FREQUENCY
prop.table(fumo.infarto)
prop.table(fumo.infarto, 1)
prop.table(fumo.infarto, 2)


chisq.test(fumo, infarto)


###       Pearson's Chi-squared test with Yates' continuity correction

data:  fumo and infarto
X-squared = 3.2793, df = 1, p-value = 0.07016


###Fisher Exact Test

> fisher.test(fumo.infarto)

###        Fisher's Exact Test for Count Data

data:  fumo.infarto
p-value = 0.04718
alternative hypothesis: true odds ratio is not equal to 1
95 percent confidence interval:
  0.9006803 57.2549701
sample estimates:
odds ratio 
  6.180528