diff --git a/docs/source/configuration.rst b/docs/source/configuration.rst
index 8b70652e..ce976624 100644
--- a/docs/source/configuration.rst
+++ b/docs/source/configuration.rst
@@ -12,7 +12,7 @@ Reference types
 When generating a report from a DataFrame, the reference type can be set with the option ``reference_type``,
 in four different ways:
 
-1. Using the DataFrame on which the stability report is built as a self-reference. This reference method is static: each time slot is compared to all the previous slots in the DataFrame (all included in one distribution). This is the default reference setting.
+1. Using the DataFrame on which the stability report is built as a self-reference. This reference method is static: each time slot is compared to all the slots in the DataFrame (all included in one distribution). This is the default reference setting.
 
     .. code-block:: python
 
@@ -40,6 +40,10 @@ in four different ways:
       # generate stability report with specific monitoring rules
       report = df.pm_stability_report(reference_type="expanding", shift=1)
 
+Note that, by default, popmon also performs a rolling comparison of the histograms in each time period with those in the
+previous time period. The results of these comparisons contain the term "prev1", and are found in the comparisons section
+of a report.
+
 
 Binning specifications
 ----------------------
@@ -53,7 +57,8 @@ To specify the time-axis binning alone, do:
 
   report = df.pm_stability_report(time_axis='date', time_width='1w', time_offset='2020-1-6')
 
-The default time width is 4 weeks ('4w'). All other features (except for 'date') are auto-binned in this example.
+The default time width is 30 days ('30d'), with time offset 2010-1-4 (a Monday).
+All other features (except for 'date') are auto-binned in this example.
 
 To specify your own binning specifications for individual features or combinations of features, do:
 
diff --git a/popmon/hist/filling/spark_histogrammar.py b/popmon/hist/filling/spark_histogrammar.py
index 560dc0ce..ad13add6 100644
--- a/popmon/hist/filling/spark_histogrammar.py
+++ b/popmon/hist/filling/spark_histogrammar.py
@@ -7,7 +7,6 @@
 """
 
 import histogrammar as hg
-import histogrammar.sparksql
 import numpy as np
 from tqdm import tqdm
 
@@ -189,8 +188,6 @@ def process_features(self, df, cols_by_type):
             to_ns = sparkcol(col).cast("timestamp").cast("float") * 1e9
             idf = idf.withColumn(col, to_ns)
 
-        hg.sparksql.addMethods(idf)
-
         return idf
 
     def construct_empty_hist(self, df, features):
@@ -218,9 +215,6 @@ def construct_empty_hist(self, df, features):
 
             hist = self.get_hist_bin(hist, features, quant, col, dt)
 
-        # set data types in histogram
-        dta = [self.var_dtype[col] for col in features]
-        hist.datatype = dta[0] if len(features) == 1 else dta
         return hist
 
     def fill_histograms(self, idf):