#####################################################################
#### Linear regression without the intercept########

library(ggplot2)

ggplot(Orange, aes(x=age, y=circumference)) + 
  geom_point(color='#2980B9', size = 4) + 
  geom_smooth(method=lm, color='#2C3E50')

library(ggplot2)

#OLS regression
fit=lm(circumference~age,data=Orange)

summary(fit)

confint(fit) #CI of intercept conatains a 0

##force intercept to be 0

fit0=lm(circumference~age+0,data=Orange)

summary(fit0)