############  One-way ANOVA #################

#Zadatak 1. Proveravamo da li postoji razlika u godinama po bracnim stanjima

install.packages("foreign") #instaliranje i ucitavanje paketa
library("foreign")

Sleep=read.spss("E:/baze/sleep4ED.sav", to.data.frame = TRUE) 
fix(Sleep) 
attach(Sleep)
 

install.packages("summarytools") # prvo zelimo da prebrojimo elemente po grupama
library("summarytools")
freq(marital)
length(marital)

library(car) #za Levinov test
leveneTest(age~marital) #p-value=0.174, imamo homogenost

# Sada kreiramo grupe kao posebne vektore 
Single=age[marital=="single"]
Married=age[marital=="married/defacto"]
Divorced=age[marital=="divorced"]
Widowed=age[marital=="widowed"]

shapiro.test(Divorced)
shapiro.test(Widowed)

library(nortest)
ad.test(Single)
ad.test(Married)

#Drugi nacin za ispitivanje normalnosti (Iz svake tabele uzimamo sta nam treba)
my_packages <- c("dplyr", "broom", "nortest")
lapply(my_packages, require, character.only = TRUE)

Sleep %>%
  group_by(marital) %>% 
  do(glance(shapiro.test(.$age))) 

Sleep %>%
  group_by(marital) %>% 
  do(glance(ad.test(.$age)))

#Posto normalnu raspodelu nemam u grupi single, primenicu ANOVA test u tri grupe u kojima imam normalnost

dat1=Sleep[marital!="single",]

model=aov(age ~ marital, data = dat1)
summary(model) #Nema razlike medju grupama

# Ako pretpostavimo da je i Single sa normalnom raspodelom, onda ne moramo da pravimo novi data frame

model1=aov(age ~ marital)
summary(model1) #sada postoji razlika

#Post hoc testovi
pairwise.t.test(age, marital, p.adj = "bonf")


# Zadatak 2. Poredimo nivo pospanosti (totsas) po starosnim grupama (agegp3)
# Baza Sleep je vec ucitana

freq(agegp3)
length(agegp3)

leveneTest(totsas~agegp3) # p-value=0.63

## SAMI PROVERITE NORMALNOST RASPODELE ###

model2=aov(totsas ~ agegp3)
summary(model2) # nema razlike

###### KRUSKAL WALLIS test

#Zadatak 3. Proveravamo da li postoji razlika u godinama po bracnim stanjima,
#ali sada necemo pretpostaviti da Single ima normalnu raspodelu

kruskal.test(age~marital, data=Sleep) # data=Sleep mozemo izostaviti ako smo attach-ovali bazu

# Naknadni testovi 

install.packages("FSA")
library(FSA)
dunnTest(age~marital, data=Sleep)