macro radlen id=100 thmin=0 thmax=0.5 zmax=600
  idn=[id]-1
  1dhist [idn] '' 100 0 100
  cmin=$sigma(cos([thmax]*3.1416/180))
  cmax=$sigma(cos([thmin]*3.1416/180))
  n/pl 10.part [cmin]<xconv(6)<[cmax] -[idn]
  nev=$hinfo([idn],sum)
  1dhist [id] '' 700 0 700
  n/pl 10.xconv(3) [cmin]<xconv(6)<[cmax] -[id]
  idi=[id]+1
  h/copy [id] [idi]
  v/del tmp*
  v/cre tmp(700)
  get/cont [id] tmp
  sigma tmp=sum(tmp)/[nev]
  put/cont [idi] tmp
  title=polar angle between [thmin] and [thmax] degrees
  title [title]
  h/pl [idi](:$rsigma([zmax]))
  set xlab 1.7
  atit 'z (cm)' 'integrated material (radiation lengths)'
  title ''
return