#!/usr/bin/env python
# -*- coding: utf-8 -*-
# The MIT License (MIT)
# Copyright (c) 2017 Juan Cabral
# Permission is hereby granted, free of charge, to any person obtaining a copy
# of this software and associated documentation files (the "Software"), to deal
# in the Software without restriction, including without limitation the rights
# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
# copies of the Software, and to permit persons to whom the Software is
# furnished to do so, subject to the following conditions:
# The above copyright notice and this permission notice shall be included in
# all copies or substantial portions of the Software.
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
# SOFTWARE.
# =============================================================================
# FUTURE
# =============================================================================
from __future__ import unicode_literals
# =============================================================================
# DOC
# =============================================================================
__doc__ = """"""
# =============================================================================
# IMPORTS
# =============================================================================
import warnings
import numpy as np
from scipy.interpolate import interp1d
from .core import Extractor, FeatureExtractionWarning
# =============================================================================
# EXTRACTOR CLASS
# =============================================================================
[docs]class StructureFunctions(Extractor):
r"""The structure function of rotation measures (RMs) contains information
on electron density and magnetic field fluctuations.
References
----------
.. [simonetti1984small] Simonetti, J. H., Cordes, J. M., & Spangler, S. R.
(1984). Small-scale variations in the galactic magnetic field-The
rotation measure structure function and birefringence in interstellar
scintillations. The Astrophysical Journal, 284, 126-134.
"""
data = ['magnitude', 'time']
features = ["StructureFunction_index_21",
"StructureFunction_index_31",
"StructureFunction_index_32"]
[docs] def fit(self, magnitude, time):
Nsf, Np = 100, 100
sf1, sf2, sf3 = np.zeros(Nsf), np.zeros(Nsf), np.zeros(Nsf)
f = interp1d(time, magnitude)
time_int = np.linspace(np.min(time), np.max(time), Np)
mag_int = f(time_int)
for tau in np.arange(1, Nsf):
sf1[tau-1] = np.mean(
np.power(np.abs(mag_int[0:Np-tau] - mag_int[tau:Np]), 1.0))
sf2[tau-1] = np.mean(
np.abs(np.power(
np.abs(mag_int[0:Np-tau] - mag_int[tau:Np]), 2.0)))
sf3[tau-1] = np.mean(
np.abs(np.power(
np.abs(mag_int[0:Np-tau] - mag_int[tau:Np]), 3.0)))
sf1_log = np.log10(np.trim_zeros(sf1))
sf2_log = np.log10(np.trim_zeros(sf2))
sf3_log = np.log10(np.trim_zeros(sf3))
if len(sf1_log) and len(sf2_log):
m_21, b_21 = np.polyfit(sf1_log, sf2_log, 1)
else:
warnings.warn(
"Can't compute StructureFunction_index_21",
FeatureExtractionWarning)
m_21 = np.nan
if len(sf1_log) and len(sf3_log):
m_31, b_31 = np.polyfit(sf1_log, sf3_log, 1)
else:
warnings.warn(
"Can't compute StructureFunction_index_31",
FeatureExtractionWarning)
m_31 = np.nan
if len(sf2_log) and len(sf3_log):
m_32, b_32 = np.polyfit(sf2_log, sf3_log, 1)
else:
warnings.warn(
"Can't compute StructureFunction_index_32",
FeatureExtractionWarning)
m_32 = np.nan
return {"StructureFunction_index_21": m_21,
"StructureFunction_index_31": m_31,
"StructureFunction_index_32": m_32}
