diff --git a/.idea/workspace.xml b/.idea/workspace.xml
index 58f8aa3..7de4edc 100644
--- a/.idea/workspace.xml
+++ b/.idea/workspace.xml
@@ -3,10 +3,7 @@
   <component name="ChangeListManager">
     <list default="true" id="d2565aa5-b0c7-4b53-9b23-84bd42c9e5d7" name="Changes" comment="">
       <change beforePath="$PROJECT_DIR$/.idea/workspace.xml" beforeDir="false" afterPath="$PROJECT_DIR$/.idea/workspace.xml" afterDir="false" />
-      <change beforePath="$PROJECT_DIR$/tests/test_opti_bayesian_cdrec.py" beforeDir="false" afterPath="$PROJECT_DIR$/tests/test_opti_bayesian_cdrec.py" afterDir="false" />
-      <change beforePath="$PROJECT_DIR$/tests/test_opti_bayesian_iim.py" beforeDir="false" afterPath="$PROJECT_DIR$/tests/test_opti_bayesian_iim.py" afterDir="false" />
-      <change beforePath="$PROJECT_DIR$/tests/test_opti_bayesian_mrnn.py" beforeDir="false" afterPath="$PROJECT_DIR$/tests/test_opti_bayesian_mrnn.py" afterDir="false" />
-      <change beforePath="$PROJECT_DIR$/tests/test_opti_bayesian_stmvl.py" beforeDir="false" afterPath="$PROJECT_DIR$/tests/test_opti_bayesian_stmvl.py" afterDir="false" />
+      <change beforePath="$PROJECT_DIR$/imputegap/contamination/contamination.py" beforeDir="false" afterPath="$PROJECT_DIR$/imputegap/contamination/contamination.py" afterDir="false" />
     </list>
     <option name="SHOW_DIALOG" value="false" />
     <option name="HIGHLIGHT_CONFLICTS" value="true" />
@@ -200,7 +197,7 @@
       <workItem from="1727357029326" duration="44000" />
       <workItem from="1727358317602" duration="1867000" />
       <workItem from="1727361217072" duration="594000" />
-      <workItem from="1727434411640" duration="14310000" />
+      <workItem from="1727434411640" duration="14424000" />
     </task>
     <servers />
   </component>
diff --git a/imputegap/contamination/contamination.py b/imputegap/contamination/contamination.py
index 66a68cb..f581cab 100644
--- a/imputegap/contamination/contamination.py
+++ b/imputegap/contamination/contamination.py
@@ -145,7 +145,7 @@ def scenario_missing_percentage(ts, series_impacted=0.2, missing_rate=0.2, prote
             W = int((N - P) * missing_rate)  # number of data to remove
 
             for to_remove in range(0, W):
-                index = P + to_remove
-                ts_contaminated.iat[series, index] = np.nan
+                I = P + to_remove
+                ts_contaminated[S, I] = np.nan
 
         return ts_contaminated