Error: unexpected '}' in "}"

Vect_fun=function(x,a) {
      if(a=1)
      {
       y= mean(x,na.rm=TRUE)
      }
      else{
        if(a=2)
        {
         y= na.aggregate(x)
        }
        else {
          y=x[!is.na(x)]
        }
      }
      y
    }