diff --git a/bamt/networks/base.py b/bamt/networks/base.py
index 1d8dadf..f9d5a79 100644
--- a/bamt/networks/base.py
+++ b/bamt/networks/base.py
@@ -486,13 +486,13 @@ def __init__(self, type: str):
             weights[tuple_key] = input_dict["weights"][str(tuple_key)]
         self.weights = weights
 
-    def fit_parameters(self, data: pd.DataFrame, dropna: bool = True, n_jobs: int = -1):
+    def fit_parameters(self, data: pd.DataFrame, n_jobs: int = -1):
         """
         Base function for parameter learning
         """
-        if dropna:
-            data = data.dropna()
-            data.reset_index(inplace=True, drop=True)
+        if data.isnull().values.any():
+            logger_network.error("Dataframe contains NaNs.")
+            return
 
         if not os.path.isdir(STORAGE):
             os.makedirs(STORAGE)
@@ -539,13 +539,15 @@ def sample(
         evidence: Optional[Dict[str, Union[str, int, float]]] = None,
         as_df: bool = True,
         predict: bool = False,
-        parall_count: int = 1,
+        parall_count: int = -1,
+        filter_neg: bool = True,
     ) -> Union[None, pd.DataFrame, List[Dict[str, Union[str, int, float]]]]:
         """
         Sampling from Bayesian Network
         n: int number of samples
         evidence: values for nodes from user
         parall_count: number of threads. Defaults to 1.
+        filter_neg: either filter negative vals or not.
         """
         from joblib import Parallel, delayed
 
@@ -632,8 +634,10 @@ def wrapper():
         positive_columns = [
             c for c in cont_nodes if self.descriptor["signs"][c] == "pos"
         ]
-        seq_df = seq_df[(seq_df[positive_columns] >= 0).all(axis=1)]
-        seq_df.reset_index(inplace=True, drop=True)
+        if filter_neg:
+            seq_df = seq_df[(seq_df[positive_columns] >= 0).all(axis=1)]
+            seq_df.reset_index(inplace=True, drop=True)
+
         seq = seq_df.to_dict("records")
         sample_output = pd.DataFrame.from_dict(seq, orient="columns")
 
@@ -816,6 +820,44 @@ def find_family(
             plot_(
                 plot_to, [self[name] for name in structure["nodes"]], structure["edges"]
             )
+    
+    def fill_gaps(self, df: pd.DataFrame, **kwargs):
+        """
+        Fill NaNs with sampled values.
+
+        :param df: dataframe with NaNs
+        :param kwargs: the same params as bn.predict
+
+        :return df, failed: filled DataFrame and list of failed rows (sometimes predict can return np.nan)
+        """
+        if not self.distributions:
+            logger_network.error("To call this method you must train parameters.")
+
+        # create a mimic row to get a dataframe from iloc method
+        list = [np.nan for _ in range(df.shape[1])]
+        df.loc["mimic"] = list
+
+        def fill_row(df, i):
+            row = df.iloc[[i, -1], :].drop(["mimic"], axis=0)
+
+            evidences = row.dropna(axis=1)
+
+            return row.index[0], self.predict(evidences, progress_bar=False, **kwargs)
+
+        failed = []
+        for index in range(df.shape[0] - 1):
+            if df.iloc[index].isna().any():
+                true_pos, result = fill_row(df, index)
+                if any(pd.isna(v[0]) for v in result.values()):
+                    failed.append(true_pos)
+                    continue
+                else:
+                    for column, value in result.items():
+                        df.loc[true_pos, column] = value[0]
+            else:
+                continue
+        df.drop(failed, inplace=True)
+        return df.drop(["mimic"]), failed
 
     def get_dist(self, node_name: str, pvals: Optional[dict] = None):
         """
diff --git a/bamt/preprocessors.py b/bamt/preprocessors.py
index 3e7acdd..847ec9c 100644
--- a/bamt/preprocessors.py
+++ b/bamt/preprocessors.py
@@ -106,15 +106,11 @@ def scan(self, data: DataFrame):
         if not columns_disc:
             logger_preprocessor.info("No one column is discrete")
 
-    def apply(self, data: DataFrame, dropna: bool = True) -> Tuple[DataFrame, Dict]:
+    def apply(self, data: DataFrame) -> Tuple[DataFrame, Dict]:
         """
         Apply pipeline
         data: data to apply on
-        dropna: drop NaNs with pandas dropna
         """
-        if dropna:
-            data = data.dropna()
-            data.reset_index(inplace=True, drop=True)
         df = data.copy()
         self.nodes_types = self.get_nodes_types(data)
         if list(self.nodes_types.keys()) != data.columns.to_list():
diff --git a/tests/test_networks.py b/tests/test_networks.py
index 582c27d..fbb060d 100644
--- a/tests/test_networks.py
+++ b/tests/test_networks.py
@@ -59,6 +59,9 @@ def prepare_bn_and_data(self):
             [("encoder", encoder), ("discretizer", discretizer)]
         )
 
+        hack_data.dropna(inplace=True)
+        hack_data.reset_index(inplace=True, drop=True)
+
         discretized_data, est = p.apply(hack_data)
 
         self.bn = HybridBN(has_logit=True)