The graph shows some "Unknown" values (ie that appear to be zero), but that's just that the API thing was unavailible at that moment. Also, the variations seem a bit weird, I'd expect something more continuous, but it appears to do some big jumps only when a block is found.
It's not continuous because once a block is going your share of it doesn't change much, assuming everyone keeps a mostly constant rate.
It jumps right after getting a new block because the initial stats are noisy and dominated by the miners luck in finding shares at that moment, also because the rate changes that happened late in the last round are no longer diluted by lots of pre-existing shares.
It would also be neat to follow the blockchain and add up all the eligius payouts for the address on the same graph.