fuelcell.datums¶

Data processing functions

fuelcell.datums.array_apply(arr, func, **kwargs)¶

Applies a function to each value in an array

Parameters

arr (array-like) – Array to which function will be applied
func (function) – function to apply to each value
**kwargs – Any other arguments required by the specified function

Returns

result – Array of the transformed values

Return type

numpy array

fuelcell.datums.avg_last_pts(arr, numpts=300)¶

Average of the last several values of an array

Auxilliary function to compute the average of an array accross the last several data points. Useful for obtaining a steady-state average.

Parameters

arr (list or numpy array) – Array of values used to compute the average.
numpts (int (default=300)) – Average is calculated using the last numpts values of the array.

Returns

avg – Average of the last several values

Return type

float

fuelcell.datums.ca_process(data=None, current_column=2, potential_column=1, area=5, reference='she', thermo_potential=0, export_data=False, save_dir='processed', threshold=5, min_step_length=50, pts_to_average=300, pyramid=False, **kwargs)¶

Processes chronoamperometry data

Can either process pre-loaded data or load and process data files. If called with no arguments, loads and processes all ‘ca’ files in the present folder. See process_steps for details on the operations performed.

Parameters

data (list of Datum) – List of Datum objects containing CA data. If unspecified, data will be loaded using ca_raw before processing.
current_column (int or str (default=1)) – Index or label of the column containing current data. Used only if automatic column identification fails
potential_column (int or str (default=2)) – Index or label of the column containing potential data. Used only if automatic column identification fails
threshold (int (default=5)) – Minimum consecutive absolute difference which constitutes a step
min_step_length (int (default=25)) – Minimum length of the arrays which result from spliting the intial array. Arrays shorter than this value will be discarded
pts_to_average (int (default=300)) – Steady-state average and sd are calculated using the last pts_to_average values of the array. Default is 300 points, which is the last 30 seconds of each hold at the instrument’s default collection rate of 10 Hz.
pyramid (bool (default=True)) – Specifies whether the current is ramped in both directions. Set pyramid=False if only ramping up or only ramping down.
area (int or float (default=5)) – Geometric active area of the MEA. Scaling factor to convert current to current density.
reference ({'she', 'sce'}, int, or float (default='she')) – Either a string identifying the reference electrode (ie ‘she’ or ‘sce’), or the potential of the reference electrode used. sce=0.241
**kwargs – Remaining arguments are passed to ca_raw to load data

fuelcell.datums.ca_raw(filename=None, folder=None, pattern='', filetype='', delimiter='\t')¶

Loads chronoamperometry data

Efficient way to load multiple chronoamperometry data files at once; equivalent to calling load_data and specifying expt_type=’ca’. If called with no arguments, loads all chronoamperometryd files in the present folder.

Parameters

filename (str, path object, or file-like (default=None)) – Full filename of a file in the present directory or a complete path to an individual file. If filename is specified, all other arguments except delimiter are ignored.
folder (str, path object, or path-like (default=None)) – Directory in which data files are stored. If none, defaults to the present directory.
pattern (str or regex) – If specified, only files matching this pattern in the specified folder are loaded. Ignored if filename is specified.
filetype (str) – Any supported filetype. Only files of the specified file type will be loaded. Can be used in conjunction with pattern or expt_type.
delimiter (char (default = ' ')) – Delimiting character if the file is a text file. Defaults to ‘ ‘ (tab-delimiting).

Returns

data – Returns a list of Datum objects, with each entry corresponding to an individual data file

Return type

list of Datum

fuelcell.datums.cp_process(data=None, current_column=2, potential_column=1, area=5, reference='she', thermo_potential=0, export_data=False, save_dir='processed', threshold=5, min_step_length=25, pts_to_average=300, pyramid=True, **kwargs)¶

Processes chronopotentiometry data

Can either process pre-loaded data or load and process data files. If called with no arguments, loads and processes all ‘cp’ files in the present folder. See process_steps for details on the operations performed.

Parameters

data (list of Datum) – List of Datum objects containing CP data. If unspecified, data will be loaded using cp_raw before processing.
current_column (int or str (default=1)) – Index or label of the column containing current data. Used only if automatic column identification fails
potential_column (int or str (default=2)) – Index or label of the column containing potential data. Used only if automatic column identification fails
threshold (int (default=5)) – Minimum consecutive absolute difference which constitutes a step
min_step_length (int (default=25)) – Minimum length of the arrays which result from spliting the intial array. Arrays shorter than this value will be discarded
pts_to_average (int (default=300)) – Steady-state average and sd are calculated using the last pts_to_average values of the array. Default is 300 points, which is the last 30 seconds of each hold at the instrument’s default collection rate of 10 Hz.
pyramid (bool (default=True)) – Specifies whether the current is ramped in both directions. Set pyramid=False if only ramping up or only ramping down.
area (int or float (default=5)) – Geometric active area of the MEA. Scaling factor to convert current to current density.
reference ({'she', 'sce'}, int, or float (default='she')) – Either a string identifying the reference electrode (ie ‘she’ or ‘sce’), or the potential of the reference electrode used. sce=0.241
**kwargs – Remaining arguments are passed to cp_raw to load data

fuelcell.datums.cp_raw(filename=None, folder=None, pattern='', filetype='', delimiter='\t')¶

Loads chronoamperometry data

Efficient way to load multiple chornopotentiometry files at once; equivalent to calling load_data and specifying expt_type=’cp’. If called with no arguments, loads all chronopotentiometry files in the present folder.

Parameters

filename (str, path object, or file-like (default=None)) – Full filename of a file in the present directory or a complete path to an individual file. If filename is specified, all other arguments except delimiter are ignored.
folder (str, path object, or path-like (default=None)) – Directory in which data files are stored. If none, defaults to the present directory.
pattern (str or regex) – If specified, only files matching this pattern in the specified folder are loaded. Ignored if filename is specified.
filetype (str) – Any supported filetype. Only files of the specified file type will be loaded. Can be used in conjunction with pattern or expt_type.
delimiter (char (default = ' ')) – Delimiting character if the file is a text file. Defaults to ‘ ‘ (tab-delimiting).

Returns

data – Returns a list of Datum objects, with each entry corresponding to an individual data file

Return type

list of Datum

fuelcell.datums.cv_process(data=None, current_column=1, potential_column=0, area=5, reference='she', thermo_potential=0, export_data=False, save_dir='processed', **kwargs)¶

Processes cyclic voltammetry data

Can either process pre-loaded data or load and process data files. If called with no arguments, loads and processes all ‘cv’ files in the present folder. Peforms the following operations in order: 1. Parse column labels to find columns containing current and potential data. If parsing fails, specified labels/indices are used 2. Convert current to current density using the specified area

Parameters

data (list of Datum) – List of Datum objects containing CV data. If unspecified, data will be loaded using cv _raw before processing.
area (int or float (default=5)) – Geometric active area of the MEA. Scaling factor to convert current to durrent density
current_column (int or str (default=1)) – Index or label of the column containing current data. Used only if automatic column identification fails
potential_column (int or str (default=0)) – Index or label of the column containing potential data. Used only if automatic column identification fails
**kwargs – Remaining arguments are passed to cv_raw to load data

fuelcell.datums.cv_raw(filename=None, folder=None, pattern='', filetype='', delimiter='\t')¶

Loads cyclic voltammetry data

Efficient way to load multiple cyclic voltammetry files at once; equivalent to calling load_data and specifying expt_type=’cv’. If called with no arguments, loads all cyclic voltammetry files in the present folder.

Parameters

filename (str, path object, or file-like (default=None)) – Full filename of a file in the present directory or a complete path to an individual file. If filename is specified, all other arguments except delimiter are ignored.
folder (str, path object, or path-like (default=None)) – Directory in which data files are stored. If none, defaults to the present directory.
pattern (str or regex) – If specified, only files matching this pattern in the specified folder are loaded. Ignored if filename is specified.
filetype (str) – Any supported filetype. Only files of the specified file type will be loaded. Can be used in conjunction with pattern or expt_type.
delimiter (char (default = ' ')) – Delimiting character if the file is a text file. Defaults to ‘ ‘ (tab-delimiting).

Returns

data – Returns a list of Datum objects, with each entry corresponding to an individual data file

Return type

list of Datum

fuelcell.datums.drop_neg(xvals, yvals)¶: Appli

fuelcell.datums.eis_process(data=None, freq_column=10, real_column=0, imag_column=1, area=5, threshold=5, min_step_length=5, export_data=False, save_dir='processed', **kwargs)¶

Processes electrochemical impedance spectroscopy data

Can either process pre-loaded data or load and process data files. If called with no arguments, loads and processes all ‘eis’ files in the present folder. Peforms the following operations in order:

Parameters

data (list of Datum) – List of Datum objects containing EIS data. If unspecified, data will be loaded using eis_raw before processing.
area (int or float (default=5)) – Geometric active area of the MEA. Scaling factor to convert current to durrent density
current_column (int or str (default=1)) – Index or label of the column containing current data. Used only if automatic column identification fails
potential_column (int or str (default=0)) – Index or label of the column containing potential data. Used only if automatic column identification fails
**kwargs – Remaining arguments are passed to cv_raw to load data

fuelcell.datums.eis_raw(filename=None, folder=None, pattern='', filetype='', delimiter='\t')¶

Loads electrochemical impedance spectroscopy data

Efficient way to load multiple electrochemical impedance spectroscopy files at once; equivalent to calling load_data and specifying expt_type=’eis’. If called with no arguments, loads all electrochemical impedance spectroscopy files in the present folder.

Parameters

filename (str, path object, or file-like (default=None)) – Full filename of a file in the present directory or a complete path to an individual file. If filename is specified, all other arguments except delimiter are ignored.
folder (str, path object, or path-like (default=None)) – Directory in which data files are stored. If none, defaults to the present directory.
pattern (str or regex) – If specified, only files matching this pattern in the specified folder are loaded. Ignored if filename is specified.
filetype (str) – Any supported filetype. Only files of the specified file type will be loaded. Can be used in conjunction with pattern or expt_type.
delimiter (char (default = ' ')) – Delimiting character if the file is a text file. Defaults to ‘ ‘ (tab-delimiting).

Returns

data – Returns a list of Datum objects, with each entry corresponding to an individual data file

Return type

list of Datum

fuelcell.datums.electrode_correct(arr, ref='she')¶

Corrects for the reference electrode

Parameters

arr (list or numpy array) – Array of potential values to which the correction will be applied
ref ({'she', 'sce'}, int, or float (default='she')) – Either a string identifying the reference electrode (ie ‘she’ or ‘sce’), or the potential of the reference electrode used. sce=0.241

fuelcell.datums.find_col(data, col_type, label=None)¶

Finds column containing the desired measurement

Parameters

data (DataFrame) – DataFrame containing the full data set
col_type (one of {'current', 'potential', 'time', 'current_err', 'potential_err', 'overpotential', 'tafelcurrent', 'realcurr', 'imagcurr'}) – Type of data being searched for
label (str or int (default=None)) – Label or index of the desired column if the column label cannot be automatically parsed

Returns

col – Array of the desired measurement values

Return type

numpy array

fuelcell.datums.find_steps(arr, threshold=5)¶

Find indices at which an array of roughly stepwise data changes values

Auxilliary function to find the points at which curren/voltage is stepped up or down during and experiment. Identifies ‘steps’ by determining the points at which the consecutive absolute difference between array values is greater than a specified threshold.

Parameters

arr (list or numpy array) – Array of roughly stepwise data
threshold (int or float (default=5)) – Minimum consecutive absolute difference which constitutes a step

Returns

splits – Indices at which the array steps up or down

Return type

numpy array

fuelcell.datums.fit_eis_linear(real, imag)¶

fuelcell.datums.fit_eis_semicircle(real, imag)¶

fuelcell.datums.load_data(filename=None, folder=None, pattern='', expt_type='', filetype='', delimiter='\t')¶

Loads data file(s) as a Datum Object

Function to load electrochemical data files as a Datum object. If called with no arguments, loads all supported data files in the present folder.

Parameters

filename (str, path object, or file-like (default=None)) – Full filename of a file in the present directory or a complete path to an individual file. If filename is specified, all other arguments except delimiter are ignored.
folder (str, path object, or path-like (default=None)) – Directory in which data files are stored. If none, defaults to the present directory.
pattern (str or regex) – If specified, only files matching this pattern in the specified folder are loaded. Ignored if filename is specified.
expt_type (str (default='')) – Alternative to specifying pattern; ignored if pattern is specified. All files containing expt_type anywhere in the file name will be loaded. Ex: to load all chronopotentiometry files, specify expt_type=’cp’.
filetype (str) – Any supported filetype. Only files of the specified file type will be loaded. Can be used in conjunction with pattern or expt_type.
delimiter (char (default = ' ')) – Delimiting character if the file is a text file. Defaults to ‘ ‘ (tab-delimiting).

Returns

data – Returns a list of Datum objects, with each entry corresponding to an individual data file

Return type

list of Datum

fuelcell.datums.lsv_process(data=None, potential_column=0, current_column=1, area=5, reference='she', thermo_potential=0, export_data=False, save_dir='processed', **kwargs)¶

Processes linear sweep voltammetry data

Can either process pre-loaded data or load and process data files. If called with no arguments, loads and processes all ‘lsv’ files in the present folder. Peforms the following operations in order:

Parameters

data (list of Datum) – List of Datum objects containing LSV data. If unspecified, data will be loaded using lsv_raw before processing.
area (int or float (default=5)) – Geometric active area of the MEA. Scaling factor to convert current to durrent density
current_column (int or str (default=1)) – Index or label of the column containing current data. Used only if automatic column identification fails
potential_column (int or str (default=0)) – Index or label of the column containing potential data. Used only if automatic column identification fails
**kwargs – Remaining arguments are passed to cv_raw to load data

fuelcell.datums.lsv_raw(filename=None, folder=None, pattern='', filetype='', delimiter='\t')¶

Loads linear sweep voltammetry data

Efficient way to load multiple linear sweep voltammetry files at once; equivalent to calling load_data and specifying expt_type=’lsv’. If called with no arguments, loads all linear sweep voltammetry files in the present folder.

Parameters

filename (str, path object, or file-like (default=None)) – Full filename of a file in the present directory or a complete path to an individual file. If filename is specified, all other arguments except delimiter are ignored.
folder (str, path object, or path-like (default=None)) – Directory in which data files are stored. If none, defaults to the present directory.
pattern (str or regex) – If specified, only files matching this pattern in the specified folder are loaded. Ignored if filename is specified.
filetype (str) – Any supported filetype. Only files of the specified file type will be loaded. Can be used in conjunction with pattern or expt_type.
delimiter (char (default = ' ')) – Delimiting character if the file is a text file. Defaults to ‘ ‘ (tab-delimiting).

Returns

data – Returns a list of Datum objects, with each entry corresponding to an individual data file

Return type

list of Datum

fuelcell.datums.overpotential_correct(arr, rxn=0)¶

Calculate overpotential

Calculates overpotential for given potential data using the specified thermodynamic potential.

Parameters

arr (list or numpy array) – Array of potential values to which the correction will be applied
ref ({'she', 'sce'}, int, or float (default='she')) – Either a string identifying the reference electrode (ie ‘she’ or ‘sce’), or the potential of the reference electrode used. sce=0.241

fuelcell.datums.process_steps(data, control_column=0, response_column=1, threshold=5, min_step_length=25, pts_to_average=300, pyramid=True, expt_type='cp', area=1, reference='she', thermo_potential=0)¶

Processes stepwise data (ex chronopotentiometry and chronoamperometry data)

Performs the following operations in order: 1. Parse column labels to find the columns containing the desired data. If automatic parsing fails, the specified column labels/indices are used. 2. Find the points at which the independent variable steps up or down using the specified threshold value. 3. Split the data at these split points. Holds with fewer than the minimum number of points are filtered out to account for outliers. Note: splitting is based upon values of the independent variable, so this will not result in the loss of meaningful data. 4. Average and standard deviation are calculated using the last several points of each step to obtain steady-state values. 5. If the indpendent variable is ramped up and down, the steady-state average and standard deviation are calculated across both the ramp-up and ramp-down holds. 6. Any necessary scaling or transformations are performed (ex. reference electrode correction, coversion to current density, etc.)

Parameters

data (DataFrame) – Dataframe containing the data to be processed
control_column (int or str (default=0)) – Label or index of the column containing the control/independent variable values
response_column (int or str (default=1)) – Label or index of the column cotaining the response/dependent variabble values
threshold (int (default=5)) – Minimum consecutive absolute difference which constitutes a step
min_step_length (int (default=25)) – Minimum length of the arrays which result from spliting the intial array. Arrays shorter than this value will be discarded
pts_to_average (int (default=300)) – Steady-state average and sd are calculated using the last pts_to_average values of the array. Default is 300 points, which is the last 30 seconds of each hold at the instrument’s default collection rate of 10 Hz.
pyramid (bool (default=True)) – Specifies whether the current is ramped in both directions. Set pyramid=False if only ramping up or only ramping down.
expt_type ({'cp', 'ca'} (default='cp')) – Specifies the type of experiment being analyzed. This is used to determine which variables are the control and response variables.
area (int or float (default=5)) – Geometric active area of the MEA. Scaling factor to convert current to current density.
reference ({'she', 'sce'}, int, or float (default='she')) – Either a string identifying the reference electrode (ie ‘she’ or ‘sce’), or the potential of the reference electrode used. sce=0.241

fuelcell.datums.semicircle(x, r, h, k)¶

fuelcell.datums.set_datum_params(data, area, ref, rxn)¶

fuelcell.datums.split_and_filter(arr, split_pts, min_length=0)¶

Split continuous array at the specified points.

Auxilliary function to split continuous current or voltage data into individual holds. Splits the array at the specified indices and discards resulting arrays which are shorter than the required minimum length.

Parameters

arr (list or numpy array) – Array to split
split_pts (int or array-like) – Indices at which to split the array
min_length (int (default=0)) – Minimum length of the arrays which result from spliting the intial array. Arrays shorter than this value will be discarded

Returns

steps – Array containing one array for each hold/step

Return type

numpy array

fuelcell.datums.split_at_zeros(xvals, yvals)¶

fuelcell.datums.std_agg(arr)¶

Aggregate standard deviations of multiple measurements.

Auxilliary function to calculate the aggregate standard deviation of multiple measuremtns. Assumes that the measurements are independent of each other

Parameters: arr (list or numpy array) – Array of standard deviations to be aggregated
Returns: sd – Aggregated standard deviation
Return type: float

fuelcell.datums.std_last_pts(arr, numpts=300)¶

Standard deviation of the last several values of an array

Auxilliary function to compute the standard deviation of an array accross the last several data points. Useful for obtaining a steady-state standard deviation.

Parameters

arr (list or numpy array) – Array of values used to compute the standard deviation.
numpts (int (default=300)) – Standard deviation is calculated using the last numpts values of the array.

Returns

sd – Standard deviation of the last several values

Return type

float

fuelcell.datums.tafel_eqn(log_curr, exchg_curr, slope)¶

fuelcell.datums.tafel_slope(log_curr, eta, min_curr=None, max_curr=None)¶