added documentation for guard peak finding

mtor/dataproc.py

@@ -113,13 +113,21 @@ def find_guard_threshold(data_frame, parameters):
     left_values = data_frame[parameters.left_guard_column]
     right_values = data_frame[parameters.right_guard_column]
     guard_values = left_values.append(right_values, ignore_index=True)
+
     guard_data = numpy.histogram(
         guard_values, bins=parameters.guard_histogram_bins
     )
+
+    # The guard edges (x-axis values) enclose the counts (y-axis values)
+    # of the histogram. This means, there is one more guard edge than count.
+    # To construct a dataframe later, the number of items must be the same.
+    # Therefore a value of 0 counts is added before the "real counts"
+    # this also solves the problem of finding the first peak value later on
+    # if the first histogram bin contains the highest count.
     guard_counts = numpy.concatenate([[0], guard_data[0]]).astype(
         numpy.float16
     )
-    guard_edges = guard_data[1]  # edges enclose the counts
+    guard_edges = guard_data[1] 
     
     pyplot.clf()
     seaborn.lineplot(x=guard_edges, y=guard_counts)