wrf.xy

wrf.xy(field, pivot_point=None, angle=None, start_point=None, end_point=None, meta=True)

Return the x,y points for a line within a two-dimensional grid.

This function is primarily used to obtain the x,y points when making a cross section.

Parameters:

  • field (xarray.DataArray or numpy.ndarray) – A field with at least two dimensions.

  • pivot_point (tuple or list, optional) – A tuple or list with two entries, in the form of [x, y] (or [west_east, south_north]), which indicates the x,y location through which the plane will pass. Must also specify angle.

  • angle (float, optional) – Only valid for cross sections where a plane will be plotted through a given point on the model domain. 0.0 represents a S-N cross section. 90.0 is a W-E cross section.

  • start_point (tuple or list, optional) – A tuple or list with two entries, in the form of [x, y] (or [west_east, south_north]), which indicates the start x,y location through which the plane will pass.

  • end_point (tuple or list, optional) – A tuple or list with two entries, in the form of [x, y] (or [west_east, south_north]), which indicates the end x,y location through which the plane will pass.

  • meta (bool, optional) – Set to False to disable metadata and return numpy.ndarray instead of xarray.DataArray. Default is True.

Returns:

An array of x,y points, which has shape num_points x 2. If xarray is enabled and the meta parameter is True, then the result will be a xarray.DataArray object. Otherwise, the result will be a numpy.ndarray object with no metadata.

Return type:

xarray.DataArray or numpy.ndarray

Examples

Example 1: Using Pivot Point and Angle

from wrf import getvar, xy
from netCDF4 import Dataset

wrfnc = Dataset("wrfout_d02_2010-06-13_21:00:00")
field = wrf.getvar(wrfnc, "slp")

# Use the center of the grid
pivot = (field.shape[-1]/2.0, field.shape[-2]/2.0)

# West-East
angle = 90.0

xy_points = xy(field, pivot_point=pivot, angle=angle)

Example 2: Using Start Point and End Point

from wrf import getvar, xy
from netCDF4 import Dataset

wrfnc = Dataset("wrfout_d02_2010-06-13_21:00:00")
field = wrf.getvar(wrfnc, "slp")

# Make a diagonal of lower left to upper right
start = (0, 0)
end = (-1, -1)

xy_points = xy(field, start_point=start, end_point=end)