1 files changed, 22 insertions, 8 deletions

diff --git a/src/argaze/GazeFeatures.py b/src/argaze/GazeFeatures.py
index 3592b13..a26b1f1 100644
--- a/src/argaze/GazeFeatures.py
+++ b/src/argaze/GazeFeatures.py
@@ -503,6 +503,9 @@ class AOIScanStep():
     aoi: str = field(default='')
     """AOI name."""
 
+    letter: str = field(default='')
+    """AOI unique letter to ease sequence analysis."""
+
     def __post_init__(self):
 
         # First movement have to be a fixation
@@ -553,24 +556,35 @@ class AOIScanPath(list):
         
         self.__movements = TimeStampedGazeMovements()
         self.__current_aoi = ''
+        self.__index = ord('A')
+        self.__aoi_letter = {}
 
     def __repr__(self):
         """String representation."""
 
         return str(super())
 
-    def __str__(self) -> str:
-        """String display."""
+    def __get_aoi_letter(self, aoi):
 
-        output = ''
+        try :
 
-        for step in self:
+            return self.__aoi_letter[aoi]
 
-            output += f'> {step.aoi} '
+        except KeyError:
 
-        output += f'> {self.__current_aoi}'
+            letter = chr(self.__index)
+            self.__aoi_letter[aoi] = letter
+            self.__index += 1
+            return letter
 
-        return output
+    def __str__(self) -> str:
+        """Convert aoi scan path into a string with unique letter per aoi step."""
+
+        sequence = ''
+        for step in self:
+            sequence += step.letter
+
+        return sequence
 
     @property
     def current_aoi(self):
@@ -598,7 +612,7 @@ class AOIScanPath(list):
             try: 
 
                 # Edit new step
-                new_step = AOIScanStep(self.__movements, self.__current_aoi)
+                new_step = AOIScanStep(self.__movements, self.__current_aoi, self.__get_aoi_letter(self.__current_aoi))
 
                 # Append new step
                 super().append(new_step)