Why did you include metro stations in your study? The original quote only included train stations. The metro originally largely replaced a tram network, so the metro station density in Paris is higher than for other underground systems. I think it is very hard to find kebap shops in Paris that are not within 500 m of a metro station. This kind of dilutes the significance of your study, because I never really noticed that metro stations had a negative impact on their surrounding area (the opposite, really).
I think your study would have been much more interesting (but not that algorithmically challenging...) if you only included the large train stations in Paris.
I think your study would have been much more interesting (but not that algorithmically challenging...) if you only included the large train stations in Paris.