anchor.diff:  module plot
   implicit none
  +
  +  type titles
  +    character(:), allocatable :: title
  +    integer                   :: length
  +  end type titles
  +
   contains
   
   ! GNUPlot Terminals.
  
positive.code:   write(1,*) "set output '" // plot_name // ".tex'"
  end subroutine epslatexterm
  
  subroutine format(xlabel,ylabel,zlabel,title,fmt)
    implicit none
    character(len=*), intent(in), optional :: xlabel, ylabel, zlabel, title, fmt
  
    if (present(xlabel) .eqv. .true.) write(1,*) "set xlabel '" // xlabel // "'"
    if (present(ylabel) .eqv. .true.) write(1,*) "set ylabel '" // ylabel // "'"
    if (present(zlabel) .eqv. .true.) write(1,*) "set xlabel '" // zlabel // "'"
    if (present(title)  .eqv. .true.) write(1,*) "set title '"  // title  // "'"
    if (present(fmt)    .eqv. .true.) write(1,*) "set format '" // fmt    // "'"
  end subroutine format
  
  subroutine ticks(xticks,yticks,zticks)
    implicit none
  
negative.code:   end if columns
  end subroutine dplot3d
  
  subroutine adplot3d(dfilename,pngname,interval,step,using,nplots,title)
    implicit none
    character(len=*), intent(in)       :: dfilename, pngname
    integer, intent(in)                :: interval(2)
    integer, intent(in), optional      :: step, using(:), nplots
    character(len=*), optional         :: title(:)
    integer                            :: i, j
    character(len=len(dfilename)+4)    :: cdfilename
    ! EXPLANATION OF EVERY http://xmodulo.com/how-to-plot-using-specific-rows-of-data-file-with-gnuplot.html
    ! plot "my.dat" every A:B:C:D:E:F
    ! A: line increment
  