diff --git a/rowers/dataprep.py b/rowers/dataprep.py
index e6708ae0..6733edb3 100644
--- a/rowers/dataprep.py
+++ b/rowers/dataprep.py
@@ -545,7 +545,11 @@ def df_resample(datadf):
 def clean_df_stats(datadf, workstrokesonly=True, ignorehr=True,
                    ignoreadvanced=False):
     # clean data remove zeros and negative values
-    before = len(datadf)
+
+    before = {}
+    for workoutid in datadf['workoutid'].unique():
+        before[workoutid] = len(datadf[datadf['workoutid']==workoutid])
+
 
 
     data_orig = datadf.copy()
@@ -790,11 +794,14 @@ def clean_df_stats(datadf, workstrokesonly=True, ignorehr=True,
         except:
             pass
 
-    after = len(datadf.dropna())
-    ratio = float(after)/float(before)
+    after = {}
+    for workoutid in data_orig['workoutid'].unique():
+        after[workoutid] = len(datadf[datadf['workoutid']==workoutid].dropna())
+        ratio = float(after[workoutid])/float(before[workoutid])
+        
 
-    if ratio < 0.01 or after < 2:
-        return data_orig
+        if ratio < 0.01 or after < 2:
+            return data_orig
 
     return datadf