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A package for parsing, validating, analyzing, and simulating impedance spectra.

Reason this release was yanked:

Stable releases are now available

Project description

pyimpspec

A package for parsing, validating, analyzing, and simulating impedance spectra.

Table of contents

Installing

pyimpspec can be installed with pip.

pip install pyimpspec

Features

The sections below are merely brief descriptions of pyimpspec's features. See the Jupyter notebook for examples of those features in action.

Circuits

pyimpspec supports the creation of Circuit objects, which can be used to simulate impedance spectra or to extract information from experimental data by means of complex non-linear least squares (CNLS) fitting. The easiest way to create circuits is by letting pyimpspec parse a circuit description code (CDC). An extended CDC syntax, which makes it possible to define e.g. initial values, is also supported.

Data parsing

Several file formats are supported by pyimpspec and the data within is used to generate a DataSet object. The file formats include:

  • Files containing the data as character-separate values (CSV).
  • Spreadsheets (.xls, .xlsx, .ods).
  • Ivium data files (.idf, .ids).
  • Gamry data files (.dta).

Not all CSV files and spreadsheets are necessarily supported as-is but the parsing of those types of files should be quite flexible. The parsers expect to find at least a column with frequencies and columns for either the real and imaginary parts of the impedance, or the absolute magnitude and the phase angle/shift. The sign of the imaginary part of the impedance and/or the phase angle/shift may be negative, but then that has to be indicated in the column header with a - prefix. Additional file formats may be supported in the future.

DataSet objects can also be created from dictionaries. The contents of the DataSet can be transformed into a pandas.DataFrame object, which in turn can be used to output the data in a variety of formats (CSV, Markdown, LaTeX, etc.).

Kramers-Kronig tests

The three tests (i.e. complex, real, and imaginary) described in "A linear Kramers-Kronig transform test for immittance data validation" by Bernard A. Boukamp (Journal of the Electrochemical Society, 1995, 142, 6, pp. 1885-1894, DOI: 10.1149/1.2044210) are implemented in pyimpspec. A variant of the complex test that uses CNLS to perform the fitting is also included.

The procedure described in "A method for improving the robustness of linear Kramers-Kronig validity tests" by Michael Schönleber, Dino Klotz, and Ellen Ivers-Tiffée (Electrochimica Acta, 2014, 131, pp. 20-27, DOI: 10.1016/j.electacta.2014.01.034) is also implemented in pyimpspec.

The relevant functions return KramersKronigResult objects that include:

  • The fitted Circuit object that is generated as part of the test.
  • The pseudo chi-squared and the µ values.
  • The frequencies of the data points that were tested.
  • The complex impedances produced by the fitted circuit at each of the tested frequencies.
  • The residuals of the real and imaginary parts of the impedances.

Equivalent circuit fitting

Fitting equivalent circuits to impedance spectra is easy with pyimpspec and generates a FittingResult object. The FittingResult object includes:

  • The fitted Circuit object.
  • Information about all of the parameters (e.g. final fitted value, estimated error, and whether or not the parameter had a fixed value during fitting).
  • The frequencies that were used during the fitting.
  • The complex impedances produced by the fitted circuit at each of the frequencies.
  • The residuals of the real and imaginary parts of the impedances.
  • The MinimizerResult object returned by lmfit.

Plotting

pyimpspec includes functions for visualizing Circuit, DataSet, KramersKronigResult, and FittingResult objects. The only backend that is currently supported is matplotlib.

Contributors

See CONTRIBUTORS for a list of people who have contributed to the pyimpspec project.

License

Copyright 2022 pyimpspec developers

pyimpspec is licensed under the GPLv3 or later.

The licenses of pyimpspec's dependencies and/or sources of portions of code are included in the LICENSES folder.

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