Source code for pygmt.src.grdtrack

"""
grdtrack - Sample grids at specified (x,y) locations.
"""
import pandas as pd
from pygmt.clib import Session
from pygmt.exceptions import GMTInvalidInput
from pygmt.helpers import (
    GMTTempFile,
    build_arg_string,
    data_kind,
    fmt_docstring,
    use_alias,
)


[docs]@fmt_docstring @use_alias(V="verbose", f="coltypes", n="interpolation") def grdtrack(points, grid, newcolname=None, outfile=None, **kwargs): """ Sample grids at specified (x,y) locations. Grdtrack reads one or more grid files and a table with (x,y) [or (lon,lat)] positions in the first two columns (more columns may be present). It interpolates the grid(s) at the positions in the table and writes out the table with the interpolated values added as (one or more) new columns. A bicubic [Default], bilinear, B-spline or nearest-neighbor interpolation is used, requiring boundary conditions at the limits of the region (see ``interpolation``; Default uses "natural" conditions (second partial derivative normal to edge is zero) unless the grid is automatically recognized as periodic.) Full option list at :gmt-docs:`grdtrack.html` {aliases} Parameters ---------- points : pandas.DataFrame or str Either a table with (x, y) or (lon, lat) values in the first two columns, or a filename (e.g. csv, txt format). More columns may be present. grid : xarray.DataArray or str Gridded array from which to sample values from, or a filename (netcdf format). newcolname : str Required if ``points`` is a :class:`pandas.DataFrame`. The name for the new column in the track :class:`pandas.DataFrame` table where the sampled values will be placed. outfile : str The file name for the output ASCII file. {V} {f} {n} Returns ------- track: pandas.DataFrame or None Return type depends on whether the ``outfile`` parameter is set: - :class:`pandas.DataFrame` table with (x, y, ..., newcolname) if ``outfile`` is not set - None if ``outfile`` is set (track output will be stored in file set by ``outfile``) """ if data_kind(points) == "matrix" and newcolname is None: raise GMTInvalidInput("Please pass in a str to 'newcolname'") with GMTTempFile(suffix=".csv") as tmpfile: with Session() as lib: # Choose how data will be passed into the module table_context = lib.virtualfile_from_data(check_kind="vector", data=points) # Store the xarray.DataArray grid in virtualfile grid_context = lib.virtualfile_from_data(check_kind="raster", data=grid) # Run grdtrack on the temporary (csv) points table # and (netcdf) grid virtualfile with table_context as csvfile: with grid_context as grdfile: kwargs.update({"G": grdfile}) if outfile is None: # Output to tmpfile if outfile is not set outfile = tmpfile.name arg_str = " ".join( [csvfile, build_arg_string(kwargs), "->" + outfile] ) lib.call_module(module="grdtrack", args=arg_str) # Read temporary csv output to a pandas table if outfile == tmpfile.name: # if user did not set outfile, return pd.DataFrame try: column_names = points.columns.to_list() + [newcolname] result = pd.read_csv(tmpfile.name, sep="\t", names=column_names) except AttributeError: # 'str' object has no attribute 'columns' result = pd.read_csv(tmpfile.name, sep="\t", header=None, comment=">") elif outfile != tmpfile.name: # return None if outfile set, output in outfile result = None return result