geocat.comp.linint1#

geocat.comp.linint1(fi, xo, xi=None, icycx=0, msg_py=None)#

Interpolates from one series to another using piecewise linear interpolation across the rightmost dimension. The series may be cyclic in the X direction.

If missing values are present, then linint1 will perform the piecewise linear interpolation at all points possible, but will return missing values at coordinates which could not be used.

If any of the output coordinates xo are outside those of the input coordinates xi, the fo values at those coordinates will be set to missing (i.e. no extrapolation is performed).

Parameters:

  • fi (xarray.DataArray, numpy.ndarray) – An array of one or more dimensions. If xi is passed in as an argument, then the size of the rightmost dimension of fi must match the rightmost dimension of xi.

    If missing values are present, then linint1 will perform the piecewise linear interpolation at all points possible, but will return missing values at coordinates which could not be used.

    Note: This variable must be supplied as a xarray.DataArray in order to copy the dimension names to the output. Otherwise, default names will be used.

  • xo (xarray.DataArray, numpy.ndarray) – A one-dimensional array that specifies the X coordinates of the return array. It must be strictly monotonically increasing or decreasing, but may be unequally spaced.

    If the output coordinates xo are outside those of the input coordinates xi, then the fo values at those coordinates will be set to missing (i.e. no extrapolation is performed).

  • xi (xarray.DataArray, numpy.ndarray) – An array that specifies the X coordinates of the fi array. Most frequently, this array is one-dimensional. It must be strictly monotonically increasing or decreasing, but can be unequally spaced. If xi is multi-dimensional, then itsimensions must be the same as fi’s dimensions. If it is one-dimensional, its length must be the same as the rightmost (fastest varying) dimension of fi.

    Note: If fi is of type xarray.DataArray and xi is left unspecified, then the rightmost coordinate dimension of fi will be used. If fi is not of type xarray.DataArray, then xi becomes a mandatory parameter. This parameter must be specified as a keyword argument.

  • icycx (bool) – An option to indicate whether the rightmost dimension of fi is cyclic. This should be set to True only if you have global data, but your longitude values don’t quite wrap all the way around the globe. For example, if your longitude values go from, say, -179.75 to 179.75, or 0.5 to 359.5, then you would set this to True.

  • msg_py (numpy.number) – A numpy scalar value that represent a missing value in fi. This argument allows a user to use a missing value scheme other than NaN or masked arrays, similar to what NCL allows.

Returns:

fo (xarray.DataArray, numpy.ndarray) – The interpolated series. The returned value will have the same dimensions as fi, except for the rightmost dimension which will have the same dimension size as the length of xo. The return type will be double if fi is double, and float otherwise.

Examples

Example 1: Using linint1 with xarray.DataArray input

import numpy as np
import xarray as xr
import geocat.comp
fi_np = np.random.rand(80)  # random 80-element array
# xi does not have to be equally spaced, but it is
# in this example
xi = np.arange(80)
# create target coordinate array, in this case use the same
# min/max values as xi, but with different spacing
xo = np.linspace(xi.min(), xi.max(), 100)
# create :class:`xarray.DataArray` and chunk it using the
# full shape of the original array.
# note that xi is attached as a coordinate array
fi = xr.DataArray(fi_np,
                  dims=['x'],
                  coords={'x': xi}
                 ).chunk(fi_np.shape)
fo = geocat.comp.linint1(fi, xo, icycx=0)