Introduce variable `first_slice`

It will change if the user chooses a slice.

Overlap/eddy_graph.f90

@@ -20,7 +20,7 @@ program eddy_graph
 
   implicit none
 
-  integer rank, n_proc, delta, i, j, iostat
+  integer rank, n_proc, delta, i, j, iostat, first_slice
   integer:: n_dates = huge(0) ! number of dates to read
   integer k ! date index
   integer k_begin, k_end, k_end_main_loop
@@ -53,6 +53,8 @@ program eddy_graph
      read(unit = *, nml = main_nml)
      write(unit = *, nml = main_nml)
 
+     first_slice = 0
+
      ! Read n_slices:
 
      call new_unit(unit)
@@ -73,11 +75,12 @@ program eddy_graph
   end if
 
   call ezmpi_bcast(n_slices, root = 0)
+  call ezmpi_bcast(first_slice, root = 0)
   allocate(hshpc(n_slices), ssm(n_slices))
 
   do i = 1, n_slices
      call shpc_open(hshpc(i), trim(shpc_dir), cyclone = cyclone, &
-          slice = i - 1, pszaccess = "rb")
+          slice = first_slice + i - 1, pszaccess = "rb")
      call dbf_read_attribute_03(ssm(i)%d0, hshpc(i)%extremum, &
           hshpc(i)%extr_date, ishape = 0)
      call read_opcol(ssm(i)%ishape_last, hshpc(i)%unit, my_lbound = ssm(i)%d0)