Provided by: gmt-common_5.4.3+dfsg-1_all bug


       blockmode - Block average (x, y, z) data tables by mode estimation


       blockmode [ table ]
        -Rregion  [   -C  ]  [   -D[width][+c][+a|+l|+h  ] [  -Er|s[-] ] [  -Q ] [  -V[level] ] [
       -W[i|o][+s] ] [ -bbinary ] [ -dnodata ] [ -eregexp ] [ -fflags ] [ -hheaders ] [ -iflags ]
       [ -oflags ] [ -r ] [ -:[i|o] ]

       Note: No space is allowed between the option flag and the associated arguments.


       blockmode  reads  arbitrarily  located  (x,y,z) triples [or optionally weighted quadruples
       (x,y,z,w)] from standard input [or table] and writes to standard output mode estimates  of
       position  and  value  for  every non-empty block in a grid region defined by the -R and -I
       arguments. Either blockmean, blockmedian, or blockmode should be used as  a  pre-processor
       before  running  surface  to  avoid  aliasing  short  wavelengths. These routines are also
       generally useful for decimating or averaging (x,y,z) data. You can modify the precision of
       the  output format by editing the FORMAT_FLOAT_OUT parameter in your gmt.conf file, or you
       may choose binary input and/or output to avoid loss of precision.


              x_inc [and optionally y_inc] is the  grid  spacing.  Optionally,  append  a  suffix
              modifier. Geographical (degrees) coordinates: Append m to indicate arc minutes or s
              to indicate arc seconds. If one of the units e,  f,  k,  M,  n  or  u  is  appended
              instead,  the  increment  is assumed to be given in meter, foot, km, Mile, nautical
              mile or US survey foot, respectively, and  will  be  converted  to  the  equivalent
              degrees  longitude  at the middle latitude of the region (the conversion depends on
              PROJ_ELLIPSOID). If y_inc is given but set to 0 it will be reset  equal  to  x_inc;
              otherwise  it  will  be  converted  to  degrees latitude. All coordinates: If +e is
              appended then the corresponding max x (east) or y (north) may be slightly  adjusted
              to  fit  exactly  the  given  increment  [by  default the increment may be adjusted
              slightly to fit the given domain]. Finally, instead of giving an increment you  may
              specify  the  number  of  nodes  desired  by  appending  +n to the supplied integer
              argument; the increment is then recalculated from  the  number  of  nodes  and  the
              domain.  The  resulting  increment  value  depends  on  whether you have selected a
              gridline-registered or pixel-registered grid;  see  App-file-formats  for  details.
              Note:  if -Rgrdfile is used then the grid spacing has already been initialized; use
              -I to override the values.

       -Rxmin/xmax/ymin/ymax[+r][+uunit] (more …)
              Specify the region of interest.


       table  3 [or 4, see -W] column ASCII data table  file(s)  [or  binary,  see  -bi]  holding
              (x,y,z[,w])  data  values.  [w]  is  an optional weight for the data. If no file is
              specified, blockmode will read from standard input.

       -C     Use the center of the block as the output  location  [Default  uses  the  modal  xy
              location (but see -Q)]. -C overrides -Q.

       -D[width][+c][+a|+l|+h ]
              Perform  unweighted  mode  calculation  via  histogram binning, using the specified
              histogram width. Append +c to center bins so that their mid point is a multiple  of
              width  [uncentered].  If multiple modes are found for a block we return the average
              mode [+a].  Append +l or +h to return the low of high mode  instead,  respectively.
              If  width  is  not  given it will default to 1 provided your data set only contains
              integers. Also, for integer data and integer bin width  we  enforce  bin  centering
              (+c)  and  select  the  lowest  mode  (+l) if there are multiples. [Default mode is
              normally the Least Median of Squares (LMS) statistic].

       -E     Provide Extended report which includes s (the L1 scale of the mode), l, the  lowest
              value,  and h, the high value for each block. Output order becomes x,y,z,s,l,h[,w].
              [Default outputs x,y,z[,w]. See -W for w output.

              Provide source id s or record number r output, i.e., append the source id or record
              number  associated  with  the modal value. If tied then report the record number of
              the higher of the two values; append - to instead report the record number  of  the
              lower  value.   Note  that  both -E and -Er[-] may be specified.  For -Es we expect
              input records of the form x,y,z[,w],sid, where sid is an  unsigned  integer  source

       -Q     (Quicker) Finds mode z and mean (x,y) [Default finds mode x, mode y, mode z].

       -V[level] (more …)
              Select verbosity level [c].

              Weighted  modifier[s].  Unweighted  input and output have 3 columns x,y,z; Weighted
              i/o has 4 columns x,y,z,w.  Weights can be used  in  input  to  construct  weighted
              modal  values  for  each  block.  Weight  sums  can be reported in output for later
              combining several runs, etc. Use -W for weighted i/o, -Wi for weighted input  only,
              and  -Wo  for weighted output only. [Default uses unweighted i/o].  If your weights
              are actually uncertainties (one sigma) then append  +s  and  we  compute  weight  =

       -bi[ncols][t] (more …)
              Select native binary input. [Default is 3 (or 4 if -Wi is set)].

       -bo[ncols][type] (more …)
              Select  native  binary  output.  [Default  is  3  (or  4 if -Wo is set)]. -E adds 3
              additional columns.

       -d[i|o]nodata (more …)
              Replace input columns that equal nodata with NaN and do the reverse on output.

       -e[~]”pattern” | -e[~]/regexp/[i] (more …)
              Only accept data records that match the given pattern.

       -f[i|o]colinfo (more …)
              Specify data types of input and/or output columns.

       -h[i|o][n][+c][+d][+rremark][+rtitle] (more …)
              Skip or produce header record(s).

       -icols[+l][+sscale][+ooffset][,] (more …)
              Select input columns and transformations (0 is first column).

       -ocols[,…] (more …)
              Select output columns (0 is first column).

       -r (more …)
              Set pixel node registration [gridline]. Each block is the locus of  points  nearest
              the  grid  value location. Consider an example with -R10/15/10/15 and -I1: With the
              -r option, 10 <= (x,y) < 11 is one of 25 blocks; without it 9.5 <= (x,y) < 10.5  is
              one of 36 blocks.

       -:[i|o] (more …)
              Swap 1st and 2nd column on input and/or output.

       -^ or just -
              Print a short message about the syntax of the command, then exits (NOTE: on Windows
              just use -).

       -+ or just +
              Print  an  extensive  usage  (help)  message,  including  the  explanation  of  any
              module-specific option (but not the GMT common options), then exits.

       -? or no arguments
              Print  a  complete  usage (help) message, including the explanation of all options,
              then exits.


       The ASCII output formats of numerical data are controlled by parameters in  your  gmt.conf
       file.  Longitude  and latitude are formatted according to FORMAT_GEO_OUT, absolute time is
       under the control of FORMAT_DATE_OUT and FORMAT_CLOCK_OUT, whereas general floating  point
       values are formatted according to FORMAT_FLOAT_OUT. Be aware that the format in effect can
       lead to loss of precision in ASCII output, which can lead to various problems  downstream.
       If  you find the output is not written with enough precision, consider switching to binary
       output (-bo if available) or specify more decimals using the FORMAT_FLOAT_OUT setting.


       To find 5 by 5 minute block mode estimates  from  the  double  precision  binary  data  in
       hawaii_b.xyg and output an ASCII table, run:

              gmt blockmode hawaii_b.xyg -R198/208/18/25 -I5m -bi3d > hawaii_5x5.xyg

       To  determine  the most frequently occurring values per 5x5 block using histogram binning,
       with data representing integer counts, try

              gmt blockmode data.txt -R0/100/0/100 -I5 -r -C -D


       blockmean, blockmedian, gmt, gmt.conf, greenspline, nearneighbor, sphtriangulate, surface,


       2018, P. Wessel, W. H. F. Smith, R. Scharroo, J. Luis, and F. Wobbe