ppcpy.calibration.rayleighfit#

Functions

DP_algorithm

Recursive implementation of the Douglas-Peucker algorithm.

DouglasPeucker

Simplify signal according to Douglas-Peucker algorithm.

chi2fit

CHI2FIT Chi-2 fitting.

fit_profile

Search the clean region with rayleigh fit algorithm.

my_dist

Calculate the perpendicular distance between pointM and the line connecting pointS and pointE.

rayleighfit

smooth_signal

ppcpy.calibration.rayleighfit.rayleighfit(data_cube)[source]#
ppcpy.calibration.rayleighfit.smooth_signal(signal, window_len)[source]#
ppcpy.calibration.rayleighfit.DouglasPeucker(signal, height, epsilon, heightBase, heightTop, maxHThick, window_size=1)[source]#

Simplify signal according to Douglas-Peucker algorithm.

Parameters:

  • signal (array) – Molecule corrected signal. [MHz]

  • height (array) – Height. [m]

  • epsilon (float) – Maximum distance.

  • heightBase (float) – Minimum height for the algorithm. [m]

  • heightTop (float) – Maximum height for the algorithm. [m]

  • maxHThick (float) – Maximum spatial thickness of each segment. [m]

  • window_size (int) – Size of the average smooth window.

Returns:

Index of the signal that stands for different segments of the signal.

Return type:

sigIndx (array)

References

https://en.wikipedia.org/wiki/Ramer%E2%80%93Douglas%E2%80%93Peucker_algorithm

History:

  • 2017-12-29: First edition by Zhenping.

  • 2018-07-29: Add the height range for the searching instead of SNR restriction.

  • 2018-07-31: Add the maxHThick argument to control the maximum thickness of each output segment.

  • 2024-12-20: Direct translated from matlab with ai

ppcpy.calibration.rayleighfit.DP_algorithm(pointList, epsilon, maxHThick)[source]#

Recursive implementation of the Douglas-Peucker algorithm.

Parameters:

  • pointList (list) – List of points [[x1, y1], [x2, y2], …].

  • epsilon (float) – Maximum distance.

  • maxHThick (float) – Maximum thickness for each segment.

Returns:

Indices of simplified points.

Return type:

sigIndx (list)

ppcpy.calibration.rayleighfit.my_dist(pointM, pointS, pointE)[source]#

Calculate the perpendicular distance between pointM and the line connecting pointS and pointE.

Parameters:

  • pointM (list) – Middle point [x, y].

  • pointS (list) – Start point [x, y].

  • pointE (list) – End point [x, y].

Returns:

Distance.

Return type:

d (float)

ppcpy.calibration.rayleighfit.chi2fit(x, y, measure_error)[source]#

CHI2FIT Chi-2 fitting. All the code are translated from the exemplified code in Numerical Recipes in C (2nd Edition). Great help comes from Birgit Heese.

USAGE:

a, b, sigmaA, sigmaB, chi2, Q = chi2fit(x, y, measure_error)

INPUTS:
x: array

The length of x should be larger than 1.

y: array

The measured signal.

measure_error: array

Measurement errors for the y values.

OUTPUTS:
a: float

Intercept of the linear regression.

b: float

Slope of the linear regression.

sigmaA: float

Uncertainty of the intercept.

sigmaB: float

Uncertainty of the slope.

chi2: float

Chi-square value.

Q: float

Goodness of fit.

HISTORY:

  • 2018-08-03: First edition by Zhenping.

Authors: - zhenping@tropos.de

ppcpy.calibration.rayleighfit.fit_profile(height, sig_aer, pc, bg, sig_mol, dpIndx, layerThickConstrain, slopeConstrain, SNRConstrain, flagShowDetail=False)[source]#

Search the clean region with rayleigh fit algorithm.

Parameters:

  • height (array_like) – height [m]

  • sig_aer (array_like) – range corrected signal

  • pc (array_like) – photon count signal

  • bg (array_like) – background

  • sig_mol (array_like) – range corrected molecular signal

  • dpIndx (array_like) – index of the region calculated by Douglas-Peucker algorithm

  • layerThickConstrain (float) – constrain for the reference layer thickness [m]

  • slopeConstrain (float) – constrain for the uncertainty of the regressed extinction coefficient

  • SNRConstrain (float) – minimum SNR for the signal at the reference height

  • flagShowDetail (bool, optional) – if True, calculation information will be printed (default: False)

Returns:

(hBIndx, hTIndx) - indices of bottom and top of searched region Returns (nan, nan) if region not found

Return type:

tuple