subroutine proc_downw (Target,iuins,Display
     &,                      b,y,m,n,mu,effw,t0,dt,wrk,nwrk)

 File = ~/sas/p/downws.f Instructions for compilations see below.

 Processes a "down-weight block" on *.INS file (unit iuins)

 A down-weight block consists of records comprising a header and a number
 of instructions. The header is used to identify an instruction set,
 matching its name with the target parameter.

 The header must start with "Downweig" at column 1 followed by the
 name of the block. The name can be an asterisk as a wild-card.

 The instructions tell how to down-weight data, incl. application of a
 data window on the whole length of the records. The data may include
 the signal model array.

 Down-weighting of sections of bad data may be combined with a smooth
 transition of weights (cosine-type).

 Target     - char**  - to locate the instruction section. If empty, a lonely
                        "Downweig" is searched for.
                        Keep string short, six to eight chars.
 IUINS      - integer - instruction file unit
 Display    - char**  - If 'W' and file data, call display_ts weights
 B(M,N)     - real*8  - signal model (design matrix)
 Y(M)       - real*8  - data
 N          - integer -  0: no down-weight on B, down-weight on Y;
                            no window on B nor Y; overrules Block instruction.
                        <0: down-weight on Y, optional window on Y.
                        >0: down-weight (and window) on N columns of B and on Y.
 MU         - integer - signal length
 EFFW       - real*8  - returned: factor to be applied on RMS(Y_returned)
                        to achieve unity gain of weighting process.
 wrk(nwrk)  - real*8  - work space

 Description of Down-Weight Block. Codewords and compulsory text are bold and underlined.
 Variable parameters appear in italic. Optional parameters between [ ].

 Line#  Instruction                    Explanation
   1    Down-weight [name] [; comment]
                                 Code from column 1, spell exactly this way!
                                 (DOWNWEIG or downweig or Downweig)
                                name - Optional instruction block identifier
                                        A named block will be processed iff
                                        Target is found in name.
                                name=* to suppress name search.

  [ 2.1  [ ?DT | !DT ] [ RDC ] F[=operator]: lu,trg,recmrs,fmt,khms,itz,lddf

                                 Sampling interval, file unit, read and
                                 filter options.
                                 File is processed with Proc_f_on_rec
                                 (cf. ~hgs/sas/p/urtapu13.f),
                                 weighting is carried out with Mult_ts_ts
                                 (cf. ~hgs/sas/p/sasu061.f).

                                 ?DT - check compatible sampling rate
                                 !DT - impose data's DT on weight series.
                                 RDC - remove DC-level in residual series
                                        before downweighting.
                                        Is often necessary !
                                  F= - codeword
                            operator - operator is passed to mult_ts_ts:
                                       / - divide (else: multiply).
                                       Q - take square root of
                                            file value.
                                       0 - return weighted data with
                                            zero DC level.
                                Additional instruction records might be
                                needed due to filter options (due to lddf)

    [ 2.2... SPEC cmd p=value [p=value...]

                                Optionally under 2.1, modification commands can be added. They
                                are interpreted and processed in subroutine modify_weights
                                at the end of downws.f The weight series read in under 2.1 is

                                SPEC  (codeword) must appear in column 1.

                                Commands cmd under SPEC:

                                MOD: P=period T=residual_time W=factor

                                      Modulus function. Applies factor on weight(i) if
                                      mod( t0+i*dt, period ) = residual_time
                                      (test accuracy is period/10).
                                      Thus, every midnight value can be downweighted with
                                      a factor of 10:
                                      SPEC MOD: P=24.d0 T=0.d0 W=10.d0

 ..............................................................................................2.2] 2.1]

   3.1  nw [RDC ][..W=type [..P=window params] [..Normal..]] [..T=length] [..[1/]V[=weight] [WS!]]

                                  nw - number of records following.
                                 RDC - remove DC-level codeword.
                                        If given, DC-bias is removed from
                                        data array before window is applied.
                                  W= - window codeword.
                                type - window type-code (e.g. HANQ).
                                  P= - parameter codeword; design
                                        parameters for KAIS, DOCH and
                                        delayed-taper windows.
                              Normal - codeword. Designates that window is
                                        applied in Normal Equations only.
                                        Else: window is applied also on
                                        If windows and residuals are to be
                                        weighted differently, the instruction
                                        block for the residuals must appear
                                  T= - taper codeword
                              length - cosine taper of down-weighted
                                        section, transition length.
                                        Taper is within the limits indicated
                                        on the record lines 3...
                                  V= - Weight value codeword
                              weight - weight value
                                 1/V - Inverse weights (sigma) codeword;
                                        applies to weight values on this
                                        record line or on record lines 3..
                                 WS! - Codeword, request to compensate the weight
                                        sum. If not given, the weight value
                                        has direct bearing on the Chi^2
                                        as is usually desired.
                                       WS! does not have any effect on
                                        the weight sum of record lines 3..
                                  .. - any text. Total length of
                                        instruction: 80 chars.

   3.2...       nw weight records. Individual down-weighting of outliers or sections of
                                           input record with different variance.
                                           One of three types of downweight records selections:

   3.2.1   yyyy mm dd hh mm ss l w

   3.2.2   ... From  yyyy mm dd hh mm ss [ff]  To  yyyy mm dd hh mm ss [ffV=w
           ... All V=w

   3.2.3   # p l w

                ff - date, time, fraction of second
                                   p - sample position
                                   l - length (number of samples).
                                   w - weight value.

In Proc_Downw there is an opportunity to call display_ts after the call to proc_f_on_rec.
The  $INCLUDE-code sections with graphics are stored in gra/downws-*.fi
Empty/nongraphic code sections are stored in nogra/downws-*.fi
With graphics the compilation should be done with
   fcs downws grasas -Igra
and without graphics
   fcs downws nograsas -Igra
thus archiving to  libgrasas.a  or libnograsas.a, respectively.

For linking the following order of references is needed:
   -L~/sas/p -lsas -l[no]grasas -lsas