filter1d - Time domain filtering of 1-D time series

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] ]

filter1dis 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-Noption 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.filter1dhas options L, Q, and S for unevenly sampled data with gaps.infileMulti-column ASCII (or binary, see-b) file holding data values to be filtered.-Fsets Filtertype,typeis one ofb(oxcar),c(osine arch),g(aussian),m(edian), orp(maximum likelihood Probability estimator -- a mode estimator), and specify full filterwidthin same units as time column, OR, use-Ffnameto give the name of a one-column file of your own coefficients. Upper case typeB,C,G,M,P,Fwill use robust filter versions: i.e., replace outliers (2.5 L1 scale off median) with median during filtering.

-Dincrementis used when series is NOT equidistantly sampled. Thenincrementwill be the abscissae resolution, i.e., all abscissae will be rounded off to a multiple ofincrement. Alternatively, resample data withsample1d.-EInclude Ends of time series in output. Default loses half the filter-width of data at each end.-HInput file(s) has Header record(s). Number of header records can be changed by editing your .gmtdefaults file. If used,GMTdefault is 1 header record.-ITo ignore values; If an input value equalsignore_valit will be set to NaN.-LChecks for Lack of data condition. If input data has a gap exceedingwidththen no output will be given at that point [Default does not check Lack].-NSets 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 isn_cols= 2,t_col= 0; i.e., file has t, f(t) pairs].-Qassess Quality of output value by checking mean weight in convolution. Enterq_factorbetween 0 and 1. If mean weight <q_factor, output is suppressed at this point [Default does not check Quality].-SChecks 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].-TMake evenly spaced timesteps fromstarttostopbyint[Default uses input times].-VSelects verbose mode, which will send progress reports to stderr [Default runs "silently"].-biSelects binary input. Appendsfor single precision [Default is double]. Appendnfor the number of columns in the binary file(s).-boSelects binary output. Appendsfor single precision [Default is double].

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 usingsample1d. 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

gmt, sample1d

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