pygmt.nearneighbor

pygmt.nearneighbor(x=None, y=None, z=None, data=None, *, spacing=None, region=None, verbose=None, outfile=None, aspatial=None, coltypes=None, registration=None, search_radius=None, empty=None, sectors=None, **kwargs)[source]

Grid table data using a “Nearest neighbor” algorithm

nearneighbor reads arbitrarily located (x,y,z[,w]) triples [quadruplets] and uses a nearest neighbor algorithm to assign a weighted average value to each node that has one or more data points within a search radius centered on the node with adequate coverage across a subset of the chosen sectors. The node value is computed as a weighted mean of the nearest point from each sector inside the search radius.

Takes a matrix, xyz triples, or a file name as input.

Must provide either data or x, y, and z.

Full option list at https://docs.generic-mapping-tools.org/latest/nearneighbor.html

Aliases:

  • E = empty

  • G = outfile

  • I = spacing

  • N = sectors

  • R = region

  • S = search_radius

  • V = verbose

  • a = aspatial

  • f = coltypes

  • r = registration

Parameters

  • x/y/z (1d arrays) – Arrays of x and y coordinates and values z of the data points.

  • data (str or 2d array) – Either a data file name or a 2d numpy array with the tabular data.

  • spacing (str) –

    xinc[+e|n][/yinc[+e|n]]. x_inc [and optionally y_inc] is the grid spacing.

    • Geographical (degrees) coordinates: Optionally, append an increment unit. Choose among 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, the registration, and the domain. The resulting increment value depends on whether you have selected a gridline-registered or pixel-registered grid; see GMT File Formats for details.

    Note: If region=grdfile is used then the grid spacing and the registration have already been initialized; use spacing and registration to override these values.

  • region (str or list) – xmin/xmax/ymin/ymax[+r][+uunit]. Specify the region of interest.

  • search_radius (str) – Sets the search radius that determines which data points are considered close to a node.

  • outfile (str) – Optional. The file name for the output netcdf file with extension .nc to store the grid in.

  • verbose (bool or str) –

    Select verbosity level [Default is w], which modulates the messages written to stderr. Choose among 7 levels of verbosity:

    • q - Quiet, not even fatal error messages are produced

    • e - Error messages only

    • w - Warnings [Default]

    • t - Timings (report runtimes for time-intensive algorithms);

    • i - Informational messages (same as verbose=True)

    • c - Compatibility warnings

    • d - Debugging messages

  • aspatial (bool or str) – [col=]name[,…]. Control how aspatial data are handled during input and output. Full documentation is at https://docs.generic-mapping-tools.org/latest/gmt.html#aspatial-full.

  • coltypes (str) – [i|o]colinfo. Specify data types of input and/or output columns (time or geographical data). Full documentation is at https://docs.generic-mapping-tools.org/latest/gmt.html#f-full.

  • registration (str) – g|p. Force gridline (g) or pixel (p) node registration. [Default is g(ridline)].

emptystr

Optional. Set the value assigned to empty nodes. Defaults to NaN.

sectorsstr

Optional. *sectors*[**+mmin_sectors]|n The circular search area centered on each node is divided into sectors sectors. Average values will only be computed if there is at least one value inside each of at least min_sectors of the sectors for a given node. Nodes that fail this test are assigned the value NaN (but see -E). If +m is omitted then min_sectors is set to be at least 50% of sectors (i.e., rounded up to next integer) [Default is a quadrant search with 100% coverage, i.e., sectors = min_sectors = 4]. Note that only the nearest value per sector enters into the averaging; the more distant points are ignored. Alternatively, use -Nn to call GDALʻs nearest neighbor algorithm instead.

Returns

ret (xarray.DataArray or None) – Return type depends on whether the outfile parameter is set:

  • xarray.DataArray: if outfile is not set

  • None if outfile is set (grid output will be stored in file set by outfile)