NAME

       filter1d - Time domain filtering of 1-D time series


SYNOPSIS

       filter1d [ infile ] -F<type><width> [ -Dincrement ] [ -E ] [ -H[nrec] ]
       [ -Iignore_val ] [ -Llack_width ] [ -Nn_cols/t_col ] [ -Qq_factor  ]  [
       -Ssymmetry_factor  ]  [  -Tstart/stop/int  ]  [  -V  ]  [ -bi[s][n] ] [
       -bo[s][n] ]


DESCRIPTION

       filter1d is a general time  domain  filter  for  multiple  column  time
       series  data.   The  user  specifies the number of columns of input and
       which column is the time.  (See -N option below).  The  fastest  opera-
       tion  occurs  when the input time series are equally spaced and have no
       gaps or outliers and the special options are not needed.  filter1d  has
       options L, Q, and S for unevenly sampled data with gaps.

       infile Multi-column  ASCII (or binary, see -b) file holding data values
              to be filtered.

       -F     sets Filtertype, type is one of b(oxcar), c(osine arch),  g(aus-
              sian),  m(edian),  or p(maximum likelihood Probability estimator
              -- a mode estimator), and specify  full  filter  width  in  same
              units as time column, OR, use -Ffname to give the name of a one-
              column file of your own coefficients.  Upper case type B, C,  G,
              M,  P, F will use robust filter versions: i.e., replace outliers
              (2.5 L1 scale off median) with median during filtering.


OPTIONS

       -D     increment is used when  series  is  NOT  equidistantly  sampled.
              Then  increment  will  be  the  abscissae  resolution, i.e., all
              abscissae will be  rounded  off  to  a  multiple  of  increment.
              Alternatively, resample data with sample1d.

       -E     Include  Ends  of time series in output.  Default loses half the
              filter-width of data at each end.

       -H     Input file(s) has Header record(s).  Number  of  header  records
              can  be changed by editing your .gmtdefaults file.  If used, GMT
              default is 1 header record.

       -I     To ignore values; If an input value equals ignore_val it will be
              set to NaN.

       -L     Checks  for  Lack  of  data  condition.  If input data has a gap
              exceeding width then no output  will  be  given  at  that  point
              [Default does not check Lack].

       -N     Sets  number  of  columns in input and which column contains the
              independent variable (time). The left-most column is  #  0,  the
              right-most  is  # (n_cols - 1).  [Default is n_cols = 2, t_col =
              0; i.e., file has t, f(t) pairs].

       -Q     assess Quality of output value by checking mean weight in convo-
              lution.   Enter  q_factor  between  0  and  1.  If mean weight <
              q_factor, output is suppressed at this point [Default  does  not
              check Quality].

       -S     Checks  symmetry  of  data  about window center.  Enter a factor
              between 0 and 1.  If (  (abs(n_left  -  n_right))  /  (n_left  +
              n_right)  ) > factor, then no output will be given at this point
              [Default does not check Symmetry].

       -T     Make evenly spaced timesteps from start to stop by int  [Default
              uses input times].

       -V     Selects verbose mode, which will send progress reports to stderr
              [Default runs "silently"].

       -bi    Selects binary input.  Append s for single precision [Default is
              double].   Append  n  for  the  number  of columns in the binary
              file(s).

       -O     Selects Overlay plot mode [Default initializes a new  plot  sys-
              tem].


EXAMPLES

       To filter the data set in the file cruise.gmtd containing evenly spaced
       gravity, magnetics, topography, and distance (in m) with a 10 km  Gaus-
       sian  filter, removing outliers, and output a filtered value every 2 km
       between 0 and 100 km, try

       filter1d  cruise.gmtd  -T0/1.0e5/2000  -FG10000   -N4/3   -V   >   fil-
       tered_cruise.gmtd

       Data  along  track  often have uneven sampling and gaps which we do not
       want to interpolate using sample1d.  To find the median depth in  a  50
       km  window  every  25  km  along  the  track of cruise v3312, stored in
       v3312.dt, checking for gaps of 10km and asymmetry of 0.3, try

       filter1d v3312.dt -FM50 -T0/100000/25 -L10 -S0.3 > v3312_filt.dt


SEE ALSO

       gmt(l), sample1d(l)



VERSION                              DATE                          FILTER1D(l)

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