diff --git a/pyFTS/common/FuzzySet.py b/pyFTS/common/FuzzySet.py
index db489ee..087d6dd 100644
--- a/pyFTS/common/FuzzySet.py
+++ b/pyFTS/common/FuzzySet.py
@@ -59,7 +59,8 @@ class FuzzySet(object):
 
 
 def set_ordered(fuzzySets):
-    return [k for k in sorted(fuzzySets.keys())]
+    tmp1 = [fuzzySets[k] for k in fuzzySets.keys()]
+    return [k.name for k in sorted(tmp1, key=lambda x: x.centroid)]
 
 
 def fuzzyfy_instance(inst, fuzzySets, ordered_sets=None):
diff --git a/pyFTS/models/pwfts.py b/pyFTS/models/pwfts.py
index fe51ec6..3980122 100644
--- a/pyFTS/models/pwfts.py
+++ b/pyFTS/models/pwfts.py
@@ -395,31 +395,45 @@ class ProbabilisticWeightedFTS(ifts.IntervalFTS):
 
         return ret
 
+    def __check_point_bounds(self, point):
+        lower_set = self.partitioner.lower_set()
+        upper_set = self.partitioner.upper_set()
+        return point <= lower_set.lower or point >= upper_set.upper
+
     def forecast_ahead(self, data, steps, **kwargs):
         ret = [data[k] for k in np.arange(len(data) - self.order, len(data))]
 
         for k in np.arange(self.order - 1, steps):
 
-            if ret[-1] <= self.sets[0].lower or ret[-1] >= self.sets[-1].upper:
+            if self.__check_point_bounds(ret[-1]) :
                 ret.append(ret[-1])
             else:
-                mp = self.forecast([ret[x] for x in np.arange(k - self.order, k)])
-
+                mp = self.forecast([ret[x] for x in np.arange(k - self.order, k)], **kwargs)
                 ret.append(mp)
 
-        return ret
+        return ret[self.order:]
+
+    def __check_interval_bounds(self, interval):
+        if len(self.transformations) > 0:
+            lower_set = self.partitioner.lower_set()
+            upper_set = self.partitioner.upper_set()
+            return interval[0] <= lower_set.lower and interval[1] >= upper_set.upper
+        elif len(self.transformations) == 0:
+            return interval[0] <= self.original_min and interval[1] >= self.original_max
 
     def forecast_ahead_interval(self, data, steps, **kwargs):
 
         l = len(data)
 
-        ret = [[data[k], data[k]] for k in np.arange(l - self.order, l)]
+        start = kwargs.get('start', self.order)
+
+        sample = data[start - (self.order - 1): start + 1]
+
+        ret = [[k, k] for k in sample]
 
         for k in np.arange(self.order, steps+self.order):
 
-            if (len(self.transformations) > 0 and ret[-1][0] <= self.sets[0].lower and ret[-1][1] >= self.sets[
-                -1].upper) or (len(self.transformations) == 0 and ret[-1][0] <= self.original_min and ret[-1][
-                1] >= self.original_max):
+            if self.__check_interval_bounds(ret[-1]):
                 ret.append(ret[-1])
             else:
                 lower = self.forecast_interval([ret[x][0] for x in np.arange(k - self.order, k)], **kwargs)
@@ -427,7 +441,7 @@ class ProbabilisticWeightedFTS(ifts.IntervalFTS):
 
                 ret.append([np.min(lower), np.max(upper)])
 
-        return ret
+        return ret[self.order:]
 
     def forecast_ahead_distribution(self, ndata, steps, **kwargs):
 
@@ -490,9 +504,7 @@ class ProbabilisticWeightedFTS(ifts.IntervalFTS):
 
             ret.append(dist)
 
-        ret = ret[self.order:]
-
-        return ret
+        return ret[self.order:]
 
     def __str__(self):
         tmp = self.name + ":\n"
diff --git a/pyFTS/partitioners/partitioner.py b/pyFTS/partitioners/partitioner.py
index f9578b9..6cc5fcb 100644
--- a/pyFTS/partitioners/partitioner.py
+++ b/pyFTS/partitioners/partitioner.py
@@ -77,6 +77,12 @@ class Partitioner(object):
     def get_name(self, counter):
         return self.prefix + str(counter) if self.setnames is None else self.setnames[counter]
 
+    def lower_set(self):
+        return self.sets[self.ordered_sets[0]]
+
+    def upper_set(self):
+        return self.sets[self.ordered_sets[-1]]
+
     def plot(self, ax):
         """
         Plot the 
diff --git a/pyFTS/tests/general.py b/pyFTS/tests/general.py
index fdf9040..ca9a030 100644
--- a/pyFTS/tests/general.py
+++ b/pyFTS/tests/general.py
@@ -31,21 +31,21 @@ train_split = 2000
 test_length = 200
 
 from pyFTS.partitioners import Grid, Util as pUtil
-partitioner = Grid.GridPartitioner(data=dataset[:train_split], npart=30)
-#partitioner = Grid.GridPartitioner(data=dataset[:train_split], npart=10, transformation=tdiff)
+#partitioner = Grid.GridPartitioner(data=dataset[:train_split], npart=30)
+partitioner = Grid.GridPartitioner(data=dataset[:train_split], npart=10, transformation=tdiff)
 
 from pyFTS.common import fts,tree
 from pyFTS.models import hofts, pwfts
 
 pfts1_taiex = pwfts.ProbabilisticWeightedFTS("1", partitioner=partitioner)
-#pfts1_taiex.append_transformation(tdiff)
+pfts1_taiex.append_transformation(tdiff)
 pfts1_taiex.fit(dataset[:train_split], save_model=True, file_path='pwfts')
 pfts1_taiex.shortname = "1st Order"
 
 print(pfts1_taiex)
 
-tmp = pfts1_taiex.predict(dataset[train_split:train_split+20], type='interval',
-                          method='heuristic')
+tmp = pfts1_taiex.predict(dataset[train_split:train_split+20], type='point',
+                          method='heuristic', steps_ahead=10)
 
 
 print(tmp)