diff --git a/mlair/helpers/filter.py b/mlair/helpers/filter.py
index 9a61de715bc02e57a41ab6c2b9a62de7157acf07..2e42d4c058c51f02ca3e65ebdcd92140e286da4b 100644
--- a/mlair/helpers/filter.py
+++ b/mlair/helpers/filter.py
@@ -19,7 +19,7 @@ from mlair.helpers import to_list, TimeTrackingWrapper, TimeTracking
 class FIRFilter:
     from mlair.plotting.data_insight_plotting import PlotFirFilter
 
-    def __init__(self, data, fs, order, cutoff, window, var_dim, time_dim, station_name=None, minimum_length=0, offset=0, plot_path=None):
+    def __init__(self, data, fs, order, cutoff, window, var_dim, time_dim, station_name=None, minimum_length=None, offset=0, plot_path=None):
         self._filtered = []
         self._h = []
         self.data = data
@@ -76,6 +76,7 @@ class FIRFilter:
     def create_visualization(self, filtered, filter_input_data, plot_dates, time_dim, sampling,
                               h, minimum_length, order, i, offset, var_dim):  # pragma: no cover
         plot_data = []
+        minimum_length = minimum_length or 0
         for viz_date in set(plot_dates).intersection(filtered.coords[time_dim].values):
             try:
                 if i < len(order) - 1:
@@ -196,12 +197,11 @@ class ClimateFIRFilter(FIRFilter):
         self.apriori_diurnal = apriori_diurnal
         self._apriori_list = []
         self.sel_opts = sel_opts
-        self.minimum_length = minimum_length
         self.new_dim = new_dim
-        self.plot_path = plot_path
         self.plot_data = []
         self.extend_length_opts = extend_length_opts
-        super().__init__(data, fs, order, cutoff, window, var_dim, time_dim, station_name=station_name)
+        super().__init__(data, fs, order, cutoff, window, var_dim, time_dim, station_name=station_name,
+                         minimum_length=minimum_length, plot_path=plot_path)
 
     def run(self):
         filtered = []
@@ -742,7 +742,7 @@ class ClimateFIRFilter(FIRFilter):
                 # visualization
                 plot_data.extend(self.create_visualization(filt, d, filter_input_data, plot_dates, time_dim, new_dim,
                                                            sampling, extend_length_history, extend_length_future,
-                                                           minimum_length, h, var, extend_length_opts))
+                                                           minimum_length, h, var, extend_opts_var))
 
             # collect all filter results
             coll.append(xr.concat(filt_coll, time_dim))
diff --git a/mlair/plotting/data_insight_plotting.py b/mlair/plotting/data_insight_plotting.py
index 096163451355cb5011dbb2cf39c48c963d51c03c..581a30b16680f1faa8a13a96a6632f642370375e 100644
--- a/mlair/plotting/data_insight_plotting.py
+++ b/mlair/plotting/data_insight_plotting.py
@@ -971,7 +971,7 @@ class PlotClimateFirFilter(AbstractPlotClass):  # pragma: no cover
         """Restructure plot data."""
         plot_dict = {}
         new_dim = None
-        for i, o in enumerate(range(len(data))):
+        for i in range(len(data)):
             plot_data = data[i]
             for p_d in plot_data:
                 var = p_d.get("var")
@@ -1187,7 +1187,7 @@ class PlotFirFilter(AbstractPlotClass):  # pragma: no cover
     def _prepare_data(self, data):
         """Restructure plot data."""
         plot_dict = {}
-        for i, o in enumerate(range(len(data))):
+        for i in range(len(data)):
             plot_data = data[i]
             t0 = plot_data.get("t0")
             filter_input = plot_data.get("filter_input")