function [col] = colmap_from_flags(irank,ihybrid,idem,iscal)
  % [col] = colmap_from_flags(irank,ihybrid,idem,iscal)
  % Create a containers.Map object with particle column order.
  % Input
  %   irank       rank written?
  %   ihybrid     hybrid written?
  %   idem        DEM written?
  %   iscal       scalar written? (number of scalars)
  % Output
  %   col         column map which can be indexed by e.g. col('x')
  
  col = containers.Map('KeyType','char','ValueType','double');
  ioffset = 0;
  if irank
    col('rank') = ioffset+1;
    ioffset = ioffset+1;
  end
  if ihybrid
    col('id') = ioffset+1;
    col('x')  = ioffset+2;
    col('y')  = ioffset+3;
    col('z')  = ioffset+4;
    col('r')  = ioffset+5;
    col('rho')= ioffset+6;
    col('ax') = ioffset+7;
    col('ay') = ioffset+8;
    col('az') = ioffset+9;
    col('u')  = ioffset+10;
    col('v')  = ioffset+11;
    col('w')  = ioffset+12;
    col('ox') = ioffset+13;
    col('oy') = ioffset+14;
    col('oz') = ioffset+15;
    col('fx') = ioffset+16;
    col('fy') = ioffset+17;
    col('fz') = ioffset+18;
    col('tx') = ioffset+19;
    col('ty') = ioffset+20;
    col('tz') = ioffset+21;
    ioffset = ioffset+21;
  end
  if idem
    col('fxc') = ioffset+1;
    col('fyc') = ioffset+2;
    col('fzc') = ioffset+3;
    col('txc') = ioffset+4;
    col('tyc') = ioffset+5;
    col('tzc') = ioffset+6;
    ioffset = ioffset+6;
  end
  if iscal
    for ii=1:iscal
      col(['s',sprintf('%d',ii)]) = ioffset+1;
      col(['q',sprintf('%d',ii)]) = ioffset+2;
      ioffset = ioffset+2;
    end
  end
end