proc getrad_overtime {rmax seltext outfile} {
  set num_frames [molinfo top get numframes]
  set ofile [open "$outfile" w];

  for {set frame 0} {$frame < $num_frames} {incr frame} {
    puts $ofile "Frame: $frame"
    puts "Frame: $frame"
    animate goto $frame
    molinfo top set frame $frame
    radden $rmax $seltext $ofile
  }

  close $ofile
}

proc radden {rmax seltext ofile} {
  set r 1
  set lastr 0

      while {$r < $rmax} {
              set sel [atomselect top "$seltext and sqrt(x*x+y*y+z*z)<$r and sqrt(x*x+y*y+z*z)>= $lastr"]
      set num [$sel num]
              puts "Radius=$r Number=$num"
              set mass 0
              if {[$sel num] == 1} {
                      set mass [$sel get mass]
              } 
              if {[$sel num] > 1} {
                      set mass [eval "vecadd [$sel get mass]"]
              }
              puts $ofile "$r $mass"
              puts "$r $mass"
              incr r
              incr lastr
	      $sel delete
      }
}