title: SIR stratified by attained age with popEpi package
body: <p>I am trying to calculate SIRs by attained age using the popEpi package and I would like to stratify results by attained age (0-5; 5-10;10-15 ... 60-65; 65+).
  I cannot figure out how to get this done. For stratifying results by follow-up time, I used the following syntax:</p>
  <pre><code>c &lt;- lexpand( DatasetSMN, status = status, birth = bi_date, exit = ex_date, entry = dg_date,
                 breaks = list(per = 1960:2013, age = 1:100, fot = c(0,5,10,15,20,25,30,35,Inf)), 
                 aggre = list(fot, agegroup = age, year = per, sex) )
  
  se &lt;- sir( coh.data = c, coh.obs = 'from0to1', coh.pyrs = 'pyrs',
             ref.data = incdata, ref.rate = 'value', conf.type = &quot;univariate&quot;, 
             adjust = c('agegroup','year','sex'), print ='fot')
  </code></pre>
  <p>This works, but I don't know how to adapt this to get results stratified by attained age.</p>
  <p>Thanks in advance!</p>