# data creation

First<- c("Lars","Kari","Jonas")
Gender=c("M","F","M")
Country=c(rep("Denmark",3)) # or I could have written them all out without the rep( ) command

#Country<- c("Denmark","Denmark","Denmark") but who wants to write all that out? :-)

# create data frame with the Denmark employees
empsDK=data.frame(First,Gender,Country)
empsDK

First<- c("Pierre","Sophie")
Gender=c("M","F")
Country=c(rep("France",2))
empsFR<- data.frame(First,Gender,Country)
empsFR

# merging like structures by country and sorted
empsAll=merge(empsDK,empsFR,by="Country",all=T,sort=T)
empsAll

# but now there are "redundant" variables and more columns than we wanted
# let's try using multiple BY variables
# using all the variables as BY variables combines all vectors together like we want
# basically, if it is not in the BY statement, it will not combine those variables at all
empsAll=merge(empsDK,empsFR,by=c("First","Gender","Country"),all=T,sort=T)
empsAll


# unsorted values -- unsorted values mean that the row order is prevserved
empsAll=merge(empsDK,empsFR,by=c("First","Gender","Country"),all=T,sort=F)
empsAll

# trying with rbind( ), cbind( ), c( ) and merge( )

df1 <- data.frame(name = c("tim", "tim", "tim", "ron"), val = 1:4)
df2 <- data.frame(name = c("tim", "tim", "ron","ron"), val = 1:4)

df1
df2
rbind(df1, df2)
cbind(df1,df2)
c(df1,df2)
merge(df1, df2, by=c("name","val"), all=T)