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 operation
       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(aussian),  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 convolution.  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).

       -bo    Selects binary output. Append s for single precision [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(1gmt), sample1d(1gmt)

                                                   1 Jan 2004                                        FILTER1D(l)