added example image to readme

README.md

@@ -57,4 +57,16 @@ You can add more years by simply adding years to the command:
 
 To display all available options, type:
 
-    python main.py -h
\ No newline at end of file
+    python main.py -h
+
+## Investigation of punishments over time and gender
+
+    python plot_gender.py -h
+
+For example, we can statistically show that the prison-punishment was "invented" in 19th century.
+
+    python plot_gender.py imprison
+
+Output:
+
+![alt text](https://gitlab.cl.uni-heidelberg.de/born/obc2kg/src/imprison-gender-time.png)