Source code for pyrfu.pyrf.gradient
#!/usr/bin/env python
# -*- coding: utf-8 -*-
# 3rd party imports
import numpy as np
import xarray as xr
# Local imports
from .calc_dt import calc_dt
__author__ = "Louis Richard"
__email__ = "louisr@irfu.se"
__copyright__ = "Copyright 2020-2023"
__license__ = "MIT"
__version__ = "2.4.2"
__status__ = "Prototype"
[docs]def gradient(inp):
r"""Computes time derivative of the input variable.
Parameters
----------
inp : xarray.DataArray
Time series of the input variable.
Returns
-------
out : xarray.DataArray
Time series of the time derivative of the input variable.
Examples
--------
>>> from pyrfu import mms, pyrf
Time interval
>>> tint = ["2017-07-18T13:03:34.000", "2017-07-18T13:07:00.000"]
Spacecraft index
>>> mms_id = 1
Load magnetic field
>>> b_xyz = mms.get_data("B_gse_fgm_brst_l2", tint, mms_id)
Time derivative of the magnetic field
>>> db_dt = pyrf.gradient(b_xyz)
"""
# guess time step
delta_t = calc_dt(inp)
d_inp_dt = np.gradient(inp.data, axis=0) / delta_t
out = xr.DataArray(
d_inp_dt,
coords=inp.coords,
dims=inp.dims,
attrs=inp.attrs,
)
if "UNITS" in out.attrs:
out.attrs["UNITS"] += "/s"
return out