Hello Fortran Experts:

I am writing with another request for assistance/direction.  I have two arrays.
 One is an array of n random numbers (converted to integer).  The other is an
array of elevation, latitude and longitude values.  I would like to use the
integer values in the random array as record identifiers for the z, x, y array
to select those records and put them into a different array while maintaining
the z, x, y array with those records removed.  I have been reading about arrays
but I am new to programming and do not know how to approach this problem.  I am
using ELF90 (Essential Lahey Fortran 90).

Any suggestions would be greatly appreciated.  

I have pasted the existing code below.  This code only includes the reading in
of the elevation file and creation of the random array, as I am at a loss as to
how to proceed with the above step.

[Is there example code available that might serve as a guideline?  I couldn't
find anything related in Numerical Recipes in Fortran or Fortran 90].  

Thank you, in advance, for any suggestions and for your time.

Sincerely,

Suzanne Wechsler

--------------------------------------------------------------------------- ----

! This program is intended to do the following:
!
! (1) read in an elevation file with x, y, z coordinates;  (DONE)
! (2) count the number of records in the file; (DONE)
! (3) generate random numbers to use to match subscripts of the input records;
      (DONE)
! (4) select the records from the input file based on the subscripts and place
!      them in their own array (as validation points);  (NEED HELP)  and
! (5) maintain the array that the elements were extracted from. (NEED HELP)
!
! Input:     Spot Elevation File
! Output:   Array of randomly selected elevations
!               Spot elevation file minus the extracted elevations
!
! The following is an example of the file format for the input file:
!     -------------------------------------------------
!     Elev.     X-Coordinate    Y-Cooridinate
!     -------------------------------------------------
!     1580      404292.375       4747337
!     1600            404372.4375        4747337
!     1300            401050.6875        4747327
!     1320            401500.9063        4747327
!     1300            403091.75  4747327
!     1540            404192.3438        4747327
!     1560            404222.3438        4747327
!     780             407273.9375        4747327
!
--------------------------------------------------------------------------
--------
program rn
implicit none
INTEGER :: nrandom, i, j, norig
REAL, allocatable :: random(:)
REAL, allocatable :: subr(:)
INTEGER, allocatable :: subi(:)
REAL, DIMENSION(10000,3) :: xyzorig ! 3D array - 10000 rows, 3 columns
! REAL, DIMENSION(10000,3) :: validpt - This would be the records selected from
xyzorig
! REAL, DIMENSION(10000,3) :: newxyz - This would be the xyzorig without the
validpt data
CHARACTER (LEN=12) :: origxyz
!
--------------------------------------------------------------------------
--------
! nrandom      = number of random values to extract from the spot elevation
file
! norig        = number of records in the original spot elevation file
! subscript()  = list of random numbers
! origxyz      = original spot elevation file
! xyzorig()    = array of original spot elevation file
!
--------------------------------------------------------------------------
--------
write (*,'(1x,a)', advance='no')"Enter the number of random numbers to
generate:   "
READ  (*,*)  nrandom
write (*,'(1x,a)', advance='no')"Enter the spot elevation file:   "
READ (*,'(a)') origxyz
!write (*,'(1x,a)', advance='no')"Enter the name for the validation point file:
  "
!READ (*,'(a)') validxyz
open (1, FILE=origxyz, STATUS='old')
!
--------------------------------------------------------------------------
-----------------
! Read in spot elevation file and count number of records in file
!
--------------------------------------------------------------------------
-----------------
norig=0
do i=1, 10000
READ(1,*,END=30) (xyzorig(i,j), j=1,3)
norig=norig+1
end do
30 do i=1, norig
WRITE(*,*) (xyzorig(i,j), j=1,3)
end do
write (*,*)"The number of records in the input file is: ", norig
!
--------------------------------------------------------------------------
-----------------
! Generates 10,000 random numbers in a range of 0 to 1
!
--------------------------------------------------------------------------
-----------------
ALLOCATE (random(nrandom))
ALLOCATE (subr(nrandom))         ! arrays allocated size of nrandom
ALLOCATE (subi(nrandom))
if (nrandom > norig) THEN
WRITE (*,*) "The number of random numbers requested exceeds values in input
file."
GO TO 250
end if
write (*,*) "Selecting random numbers........"
call random_seed()               ! initializes the random number generator
do i=1, nrandom
call random_number(random)
END do
!
--------------------------------------------------------------------------
-----------------
! Convert random numbers from 0-1 range to range consistent with input file
!
--------------------------------------------------------------------------
-----------------
subr=random*norig
subi=INT(subr)+1
WRITE (*,*) "The records to be randomly removed are:", subi(1:nrandom)  !writes
"nrandom" random numbers as integers
!
--------------------------------------------------------------------------
-----------------
! Select records from input file based on random subscripts in subi()
!
--------------------------------------------------------------------------
-----------------

This is what I don't know how to do.........

!
--------------------------------------------------------------------------
-----------------
! Remove elevations of subscripts corresponding to subi from original array
into new array
!
--------------------------------------------------------------------------
-----------------

!
--------------------------------------------------------------------------
-----------------
! Save array with records removed
!
--------------------------------------------------------------------------
-----------------