title: R: splitting long zoo time series into calendar
body: <p>I have a several-year length zoo object.</p>
  
  <p>This is a time series of daily quotes (first column : date, second column : quote)</p>
  
  <p>I wish to split this long time series into calendar year subsets, the ultimate goal being to plot those data in a single chart, the horizontal axis of which being one year-length.</p>
  
  <p>(I don't want to convert my source daily data into monthly ones or any other timestep ...).</p>
  
  <p>Thank you.   </p>