tafla <- SB %>% group_by(stod, arstid) %>%
  summarise(Medaltal_sol = round(mean(sol_klst, na.rm  = T),2),
  Stadalfravik_sol = round(sd(sol_klst, na.rm  = T),2),
  Medaltal_urk = round(mean(heild_urk),2),
  Stadalfravik_urk = round(sd(heild_urk),2),
  Medaltal_vind = round(mean(vindhradi),2),
  Stadalfravik_vind = round(sd(vindhradi),2))