New config function cov

CHANGELOG.md

@@ -12,11 +12,12 @@ SPDX-License-Identifier: GPL-3.0-or-later
 - Methods `logicalAnd` and `logicalOr`
 - `Flags` supports slicing and column selection with `list` or a `pd.Index`
 - Expose the `History` via `SaQC._history_`
+- Config function `cov` (coefficient of variation)
 ### Changed
 - Deprecate `interpolate`, `linear` and `shift` in favor of `align`
 - Deprecate `roll` in favor of `rolling`
 - Rename `interplateInvalid` to `interpolate`
-- Rename `interpolateIndex` to `align` 
+- Rename `interpolateIndex` to `align`
 - Deprecate `flagMVScore` parameters: `partition_min` in favor of `window`, `partition_min` in favor of `min_periods`, `min_periods` in favor of `min_periods_r`
 ### Removed
 - Parameter `limit` from `align`
@@ -35,9 +36,9 @@ SPDX-License-Identifier: GPL-3.0-or-later
 - python 3.11 support
 - added Local Outlier Factor functionality
 ### Changed
-- Remove all flag value restrictions from the default flagging scheme `FloatTranslator` 
-- Renamed `TranslationScheme.forward` to `TranslationScheme.toInternal` 
-- Renamed `TranslationScheme.backward` to `TranslationScheme.toExternal` 
+- Remove all flag value restrictions from the default flagging scheme `FloatTranslator`
+- Renamed `TranslationScheme.forward` to `TranslationScheme.toInternal`
+- Renamed `TranslationScheme.backward` to `TranslationScheme.toExternal`
 - Changed default value of the parameter `limit` for `SaQC.interpolateIndex` and `SaQC.interpolateInvalid` to ``None``
 - Changed default value of the parameter ``overwrite`` for ``concatFlags`` to ``False``
 - Deprecate ``transferFlags`` in favor of ``concatFlags``
@@ -72,7 +73,7 @@ SPDX-License-Identifier: GPL-3.0-or-later
 ### Removed
 - `closed` keyword in `flagJumps`
 ### Fixed
-- fixed undesired behavior in `flagIsolated` for not harmonized data 
+- fixed undesired behavior in `flagIsolated` for not harmonized data
 - fixed failing translation of `dfilter`-defaults
 - fixed unbound recursion error when interpolating with order-independent methods in `interpolateIndex`
 - fixed not working min_periods condition if `window=None` in `assignZScore`

saqc/parsing/environ.py

@@ -7,6 +7,7 @@
 # -*- coding: utf-8 -*-
 
 import numpy as np
+import pandas as pd
 import scipy.stats as st
 
 import saqc.lib.ts_operators as ts_ops
@@ -21,6 +22,14 @@ def zscore(obj):
     return st.zscore(obj, nan_policy="omit")
 
 
+def cv(series: pd.Series) -> pd.Series:
+    """
+    calculates the coefficient of variation on a min-max scaled time series
+    """
+    series_ = (series - series.min()) / (series.max() - series.min())
+    return series_.std() / series_.mean()
+
+
 ENVIRONMENT = {
     # Infinity constant
     "inf": np.inf,
@@ -50,6 +59,8 @@ ENVIRONMENT = {
     "std": np.nanstd,
     # Variance. Ignores NaN.
     "var": np.nanvar,
+    # Coefficient of variation.
+    "cv": cv,
     # Median. Ignores NaN.
     "median": np.nanmedian,
     # Count Number of values. Ignores NaNs.