Added statistics.

README.md

@@ -17,6 +17,16 @@ Currently we support the following datasest:
 The details about each dataset can be found in the README files in the
 datasets subdirectories.
 
+## Statistics
+
+Dataset   | Number of trees | Avg. tree size | Min tree size | Max tree size | Number of distinct labels
+----------|-----------------|----------------|---------------|---------------|-------------------------- 
+Bolzano   | 299             | 166            | 2             | 2105          | 592
+DBLP      | 3934134         | 25             | 8             | 2986          | 14664605
+Python    | 150000          | 946            | 1             | 46481         | 3523697
+Sentiment | 9645            | 37             | 3             | 103           | 19470
+Swissprot | 556196          | 862            | 101           | 48286         | 11439467
+
 ## Repository organisation
 
 Each dataset and its corresponding scripts belong to a separate directory with a name identifying the dataset.