1 files changed, 28 insertions, 2 deletions
diff --git a/src/argaze/GazeFeatures.py b/src/argaze/GazeFeatures.py
index a098dc4..21841ac 100644
--- a/src/argaze/GazeFeatures.py
+++ b/src/argaze/GazeFeatures.py
@@ -548,18 +548,22 @@ AOIScanPathType = TypeVar('AOIScanPathType', bound="AOIScanPathType")
 # Type definition for type annotation convenience
 
 class AOIScanPath(list):
-    """List of aoi scan steps over successive AOI."""
+    """List of aoi scan steps over successive aoi."""
 
-    def __init__(self):
+    def __init__(self, expected_aois: list[str] = []):
 
         super().__init__()
         
+        self.__expected_aois = expected_aois
         self.__movements = TimeStampedGazeMovements()
         self.__current_aoi = ''
         self.__index = ord('A')
         self.__aoi_letter = {}
         self.__letter_aoi = {}
 
+        size = len(self.__expected_aois)
+        self.__transition_matrix = pandas.DataFrame(numpy.zeros((size, size)), index=self.__expected_aois, columns=self.__expected_aois)
+
     def __repr__(self):
         """String representation."""
 
@@ -593,11 +597,23 @@ class AOIScanPath(list):
         return sequence
 
     @property
+    def expected_aois(self):
+        """List of all expected aoi."""
+
+        return self.__expected_aois
+    
+    @property
     def current_aoi(self):
         """AOI name of aoi scan step under construction"""
 
         return self.__current_aoi
 
+    @property
+    def transition_matrix(self) -> pandas.DataFrame:
+        """Pandas DataFrame where indexes are transition departures and columns are transition destinations."""
+
+        return self.__transition_matrix
+
     def append_saccade(self, ts, saccade):
         """Append new saccade to aoi scan path."""
 
@@ -612,6 +628,10 @@ class AOIScanPath(list):
         .. warning::
            It could raise AOIScanStepError"""
 
+        if looked_aoi not in self.__expected_aois:
+
+            raise AOIScanStepError('AOI not expected', looked_aoi)
+
         # Is it fixation onto a new aoi?
         if looked_aoi != self.__current_aoi and len(self.__movements) > 0:
 
@@ -626,6 +646,12 @@ class AOIScanPath(list):
                 # Edit new step
                 new_step = AOIScanStep(self.__movements, self.__current_aoi, letter)
 
+                # Edit transition matrix
+                if len(self) > 0:
+
+                    # Increment [index: source, columns: destination] value
+                    self.__transition_matrix.loc[self[-1].aoi, self.__current_aoi,] += 1
+
                 # Append new step
                 super().append(new_step)