fillna=False when pivoting df in collection.to_df
@@ -114,7 +114,7 @@ class BIDSVariableCollection(object):
ind_cols = list(set(df.columns) - {'condition', 'amplitude'})
df = df.pivot_table(index=ind_cols, columns='condition',
- values='amplitude', aggfunc='first')
+ values='amplitude', aggfunc='first', dropna=False)
df = df.reset_index().fillna(fillna)
df.columns.name = None
return df
