function series rel_ok (const series obsdate, const series reldate, int p)
  series y_obs, m_obs, d_obs, y_rel, m_rel, d_rel
  isoconv(obsdate, &y_obs, &m_obs, &d_obs)
  isoconv(reldate, &y_rel, &m_rel, &d_rel)
  series dm = (12*y_rel + m_rel) - (12*y_obs + m_obs)
  return dm < p || (dm == p && d_rel <= d_obs)
end function

nulldata 45
setobs 12 2005:10

string fname = "INDPRO.txt"

# initial published values
join @fname firstpub --data=INDPRO --tkey=observation_date \
--tconvert=realtime_start_date --aggr=min(realtime_start_date)

# plus 3 months
join @fname plus3 --data=INDPRO --tkey=observation_date \
--tconvert="observation_date,realtime_start_date" \
--filter="rel_ok(observation_date, realtime_start_date, 3)" \
--aggr=max(realtime_start_date)

# plus 6 months
join @fname plus6 --data=INDPRO --tkey=observation_date \
--tconvert="observation_date,realtime_start_date" \
--filter="rel_ok(observation_date, realtime_start_date, 6)" \
--aggr=max(realtime_start_date)

# plus 12 months
join @fname plus12 --data=INDPRO --tkey=observation_date \
--tconvert="observation_date,realtime_start_date" \
--filter="rel_ok(observation_date, realtime_start_date, 12)" \
--aggr=max(realtime_start_date)

setinfo firstpub --graph-name="First publication"
setinfo plus3 --graph-name="Plus 3 months"
setinfo plus6 --graph-name="Plus 6 months"
setinfo plus12 --graph-name="Plus 12 months"

# set --output=realtime.pdf for PDF
gnuplot firstpub plus3 plus6 plus12 --time --with-lines \
 --output=display { set key left bottom; }