Two early examples of analysis:
jphysiol_80_3_1042.png see https://bitbucket.org/petermr/diagramanalyzer/src/e837eb25c124f05483e0a95d9c8ef1947b00a849/src/test/resources/org/xmlcml/diagrams/neuro/jphysiol_80_3_1042.png?raw=true This is a voltage-current trace with all the characters (axes, etc.) stripped off.
