NAME
     ZF - NMRPipe Zero Fill

SYNOPSIS
     nmrPipe -fn ZF [-zf zfCnt | -pad padCnt | -size finalSize  |
     -inv] [-mid] [-auto]

DESCRIPTION
     ZF extends the data size by appending  zeros.   It  is  used
     primarily  on time-domain data to increase the digital reso-
     lution of the corresponding spectrum.  In addition, doubling
     the original data size by zero filling is required if a Hil-
     bert Transform (HT) will be used later to  reconstruct  ima-
     ginary data.

     There are several ways to specify the amount of zero filling
     to  perform.   By  default,  ZF  will double the size of the
     data.

OPTIONS
     -zf zfCount
          Specifies the number of times to double the  data  size
          by zero filling. The default value is 1.

     -pad padCount
          Specifies the number of zeros to add to  the  data,  in
          complex points; it is an alternative to -zf and -size.

     -size finalSize
          Specifies the desired complex size of  the  data  after
          zero filling; it is an alternative to -zf and -pad.

     -mid This flag will cause the zeros to be inserted into  the
          middle  of  the data, rather than being appended to the
          end.

     -auto
          This flag will round the final zero-fill size specified
          by  the  other  options up to the nearest power of two.
          This will speed up Fourier transform steps  which  fol-
          low,  but  it  may  increase the data size to an incon-
          veniently large value.

     -inv This flag  is  used  on  inverse-processed  time-domain
          data,  to  remove zeros which were appended in previous
          zero-fill steps.  It reduces the data size to the valid
          time-domain size recorded in the header.

EXAMPLES
     Double the data size by zero filling:

        nmrPipe -fn ZF
        nmrPipe -fn ZF -zf 1


     Double the data size, and round up to a power of two:

        nmrPipe -fn ZF -auto
        nmrPipe -fn ZF -zf 1 -auto


     Increase the data size by a factor of 4:

        nmrPipe -fn ZF -zf 2

     Zero fill to 1024 complex points:

        nmrPipe -fn ZF -size 1024

     Extend the data size by appending 1 complex point:

        nmrPipe -fn ZF -pad 1

     Remove any zero-fill performed previously:

        nmrPipe -fn ZF -inv


HEADER VALUES
     ZF updates the data size (NDSIZE) to reflect  the  new  data
     size,  points,  and  updates  the  zero  fill size (NDZF) to
     reflect the amount of zero filling performed.

     ZF also updates some chemical shift calibration  information
     (NDCENTER and NDORIG) to accommodate the new position of the
     zero-frequency  point   which   is   anticipated   for   the
     corresponding spectrum.

     In inverse mode (-inv), the data  size  is  reduced  to  the
     recorded valid time-domain size (NDAPOD).

SEE ALSO
     fdatap.h, HT(1), FT(1)

BUGS
     Chemical shift calibration information may  not  be  updated
     correctly   for   spectral   regions  which  are  extracted,
     inverse-processed, and re-processed with zero-filling.