Fortran: Add column per column to file - fortran

Question

The code consists of a do-loop and creates arrays of data as long as running. I need these arrays added to a file as new columns.
The first column is fixed (wavelengths) and the second is generated within the first run:
OPEN (unit=11,file=filename // '.csv')
WRITE(11,'(i4,A1,f10.6)') (lambda(ii),tab,resv(ii), ii=1,nw)
CLOSE(11)
lambda are the wavelengths (4 digits), tab is declared as char(9) and resv are my data (floating). The array consists of nw=2000 items.
First time running the script gives me a nice output which I can load into MS Excel as .csv
However, the script is to return to the beginning of the loop, calculate new data and store the changed "resv" items into a new column.
But when I go like
WRITE(11,'(T17,i4,A1,f10.6)') (lambda(ii),tab,resv(ii), ii=1,nw)
the new data is indeed stored into column 17, but all the data before is being removed!
So how can I tell Fortran to "add" a new column?

Answer 1

Try a variant of this. Have a look at the code in addcolumn. The restriction is that your line can't be more than 1024 characters long. You can increase the size of the array to suit your needs.
module mod_helper
integer, parameter:: AMAX = 10
integer, dimension(AMAX):: coldata
integer:: revision
contains
subroutine init
revision = 0
do ii = 1, AMAX
coldata(ii) = ii
end do
end subroutine init
subroutine increment(howmuch)
integer, intent(in):: howmuch
coldata = coldata + howmuch
end subroutine
subroutine addcolumn(csvname)
character*(*), intent(in) csvname
integer(kind=2):: status
integer:: prevlen
character(1024):: prev, oldname, newname
integer, parameter:: oldfile = 20, newfile = 30
write(oldname, "(A,I3.3,'.csv')") csvname, revision
revision = revision + 1
write(newname, "(A,I3.3,'.csv')") csvname, revision
if (revision .gt. 1) then
! Open the old file
open(oldfile, file=oldname, access="sequential", status="old")
end if
open(newfile, file=newname, access="sequential", status="new", action="write")
prev = ' '
do ii = 1, AMAX
if (revision .gt. 1) then
! read previous contents as a string
read(oldfile, "(A)") prev
prevlen = len(trim(prev))
else
prevlen = 1
end if
! write previous and new contents
write(newfile, "(A, I4, ',')") prev(1:prevlen), coldata(ii)
end do
! delete the previous file
if (revision .gt. 1) close(oldfile, status='delete')
close(newfile)
end subroutine
end module
program main
use mod_helper
call init
call addcolumn('col')
call increment(1)
call addcolumn('col')
call increment(20)
call addcolumn('col')
end program