library(foreign)
col_regfile09 <- read.dta("col_regfile09.dta")
#isolamento di un singolo anno
data06 <- col_regfile09[col_regfile09$year==2006,]
#scelta variabili,selezione colonne
data06 <- data06[,c(2,3,6,8,12,27,34,4,5,29)]
#trasformazione dati
#casi completi
data06 <- data06[complete.cases(data06)==TRUE,]
#eliminazione dei flussi uguali a zero
Gravity_zeros <- data06[data06$flow != 0,]
row.names(Gravity_zeros) <- 1:length(row.names(Gravity_zeros))
#dividi il PIL per 1mln, per scalare
Gravity_zeros$gdp_o <- Gravity_zeros$gdp_o / 1000000
Gravity_zeros$gdp_d <- Gravity_zeros$gdp_d / 1000000

Gravity_no_zeros <- data06[data06$flow != 0,]


library(gravity)
data(Gravity_zeros)
str(Gravity_zeros)


##OLS METHOD##
OLS(y="flow", dist="distw", x=c("comlang_off", "rta", "comcur", "contig"),
          inc_o="gdp_o", inc_d="gdp_d", uie=FALSE, vce_robust=TRUE, 
          data=Gravity_no_zeros)

##FIXED EFFECTS##
Fixed_Effects(y="flow", dist="distw", fe=c("iso_o", "iso_d"),
    x=c("comcur") vce_robust=TRUE, data=Gravity_no_zeros)


#DOUBLE DEMEANING
DDM(y="flow", dist="distw", x=c("rta", "comcur", "contig"),
              vce_robust=TRUE, data=Gravity_no_zeros)

#BONUS VETUS OLS(BVU,BVW)
BVU(y="flow", dist="distw", x=c("rta", "comlang_off"),
              inc_o="gdp_o", inc_d="gdp_d" vce_robust=TRUE, 
              data=Gravity_no_zeros)

BVW(y="flow", dist="distw", x=c("rta", "comlang_off", "contig"),
    inc_o="gdp_o", inc_d="gdp_d" vce_robust=TRUE, 
    data=Gravity_no_zeros)