filter1d

       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] ]

DESCRIPTION

       filter1d is a general time domain filter for multiple col­
       umn  time  series  data.  The user specifies the number of
       columns of input and which column is the  time.   (See  -N
       option below). The fastest operation occurs when the input
       time series are equally spaced and have no  gaps  or  out­
       liers  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(aussian),  m(edian), or p(maximum likeli­
              hood 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  ver­
              sions:  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 res­
              olution, 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 .gmt­
              defaults  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].
              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  convolution.   Enter q_factor between 0
              and 1. If mean weight < q_factor,  output  is  sup­
              pressed at this point [Default does not check Qual­
              ity].

       -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).

       -bo    Selects binary output. Append s for  single  preci­
              sion [Default is double].

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 Gaussian 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 >
       filtered_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)