######################poisson regression-example1####################
data1<-read.table(file="/Users/macbook/Documents/Fatemeh/Fati-Old-PC/examine/categgorical data/R-program/poisson regression/data2.txt",header=T)

x<-data1$x
y<-data1$y
plot(x,y,pch=16)

model1=glm(y~x,family=poisson(link=log))
summary(model1)

anova(model1)

anova(model1,test="Chisq")
######################poisson regression####################
data<-read.table(file="/Users/macbook/Documents/Fatemeh/Fati-Old-PC/examine/categgorical data/R-program/poisson regression/data.txt")
dim(data)
y=data$V5
x1=data$V2
x2=data$V3
x3=data$V4

x2<-as.factor(x2)

model1=glm(y~x1+x2+x3,family=poisson(link=log))
summary(model1)

c.x2<-coef(model1)[3]

exp(c.x2) # odds ration 
1/exp(c.x2)

exp(confint(model1))



x22<-relevel(x2,ref="small")
x22

model2=glm(y~x1+x22+x3,family=poisson(link=log))
summary(model2)

model3=glm(y~x1*x3+x2,family=poisson(link=log))
summary(model3)