diff --git a/graph.py b/graph.py
index 18fb788..309b167 100644
--- a/graph.py
+++ b/graph.py
@@ -13,7 +13,7 @@ class PDGraphPeers():
     def unique_peers_counts(self):
         return self.df.groupby(['Peer'])['Date'].nunique()
 
-    def number_of_days(self, exclude=20):
+    def days_per_peers(self, exclude=20):
         nu_peers = self.unique_peers_counts()
         ex_twenty_day = nu_peers[nu_peers > exclude]
         ax = sns.distplot(ex_twenty_day, kde=False, hist=True)
@@ -22,4 +22,47 @@ class PDGraphPeers():
             xlabel='# of days', 
             ylabel='# of peers'
         )
-        return ax.get_figure()
+        return ax
+
+    def weekly_cohorts(self):
+        self.df['datetime'] = pd.to_datetime(self.df['Date'])
+        self.df['week'] = self.df['datetime'].dt.to_period('W')
+        self.df['month'] = self.df['datetime'].dt.to_period('M')
+        self.df['cohort'] = self.df.groupby('Peer')['datetime'].transform('min').dt.to_period('W')
+        df_cohort = self.df.groupby(['cohort', 'week']).agg(n_peers=('Peer', 'nunique')).reset_index(drop=False)
+
+        df_cohort['period_number'] = (
+            df_cohort.week - df_cohort.cohort).apply(attrgetter('n')
+        )
+        cohort_pivot = df_cohort.pivot_table(
+            index = 'cohort',
+            columns = 'period_number',
+            values = 'n_peers'
+        )
+        cohort_size = cohort_pivot.iloc[:,0]
+        retention_matrix = cohort_pivot.divide(cohort_size, axis = 0)
+
+        fig, ax = plt.subplots(1, 2, figsize=(12, 8), sharey=True, gridspec_kw={'width_ratios': [1, 11]})
+        
+        # retention matrix
+        sns.heatmap(retention_matrix, 
+                    mask=retention_matrix.isnull(), 
+                    annot=True, 
+                    fmt='.0%', 
+                    cmap='RdYlGn', 
+                    ax=ax[1])
+        ax[1].set_title('Weekly Cohorts: Peer Retention', fontsize=16)
+        ax[1].set(xlabel='# of periods',
+                  ylabel='')
+
+        # cohort size
+        cohort_size_df = pd.DataFrame(cohort_size).rename(columns={0: 'cohort_size'})
+        white_cmap = mcolors.ListedColormap(['white'])
+
+        fig.tight_layout()
+        return sns.heatmap(cohort_size_df, 
+                    annot=True, 
+                    cbar=False, 
+                    fmt='g', 
+                    cmap=white_cmap, 
+                    ax=ax[0])
diff --git a/main.py b/main.py
index 627a7a7..e6c120b 100755
--- a/main.py
+++ b/main.py
@@ -38,9 +38,11 @@ def main():
 
     pdg = PDGraphPeers(data)
 
-    print(pdg.unique_peers_counts())
-    plot = pdg.number_of_days()
-    plot.savefig("output.png")
+    plot = pdg.days_per_peers()
+    plot.figure.savefig("days_per_peers.png")
+
+    matrix = pdg.weekly_cohorts()
+    matrix.figure.savefig("weekly_cohorts.png")
 
 if __name__ == '__main__':
     main()
diff --git a/output.png b/output.png
deleted file mode 100644
index 5f2c8b6..0000000
Binary files a/output.png and /dev/null differ