Error on if statement within a function in R

Trying to create this function but R returns me an error

impute_age=function(row){
  if(Titanic$Pclass=="1"){
    return(Pclass1$Median_age)
  }else if(Titanic$Pclass=="1"){
    return(Pclass2$Median_age){
  else{
    return(Pclass3$Median_age)
      }
    }
  }
}