Latest Contributions by TheoAalders

I will defenitely look into the DO-thing - if it is accessible I try to implement what you have suggested! Personally, I am very happy with the .69 Pearson - I think it really depends in what field you work. In my experience a correlation of >.5 is good for everthing involving human society. Honestly, I never came across a correlation of something like .9 in social scientific studies... Thanks again for your helpe! ... View more

Ok, I couldn't stop working on this, so no here is my work-around: 1. Create distance raster based on the city boundary (here is the weakest point, since the start of the pollution does not coincide with the city boundary. 2. Convert Distance raster to polygon-feature ("distPol") Now I have something that looks like this: 3. Intersect rivers mit "distPol". Now I have a multitude of microscopic lines along the rivers, each carrying information about the distance it as to the city boundary ("riverInt") 4. Create a 500m (arbitrary) buffer around the features for wealthy areas as well as slums. This is in order to account for influences the river may have on these areas even when not directly crossing them. 5. Spatial Join of these buffers with the micro-rivers I created before ("riverInt") and summarise by average. 6. Now I have polygons carrying information about the respective average distance of rivers crossing them. 7. Quickly analyse the correlation and, tadaa, Pearson of 0,69, and p-value of practically 0. Wealthy areas tend to be upstream of rivers while slum areas tend to be downstream. Qed. I am now thinking about improving the city-boundary solution. I decided not to take the source of each river, because a) some sources are many kilometers away, i.e. not on the map; b) it assumes that each river has the same pollution-gradient, which is not true. A river that starts near an industrial area is probably highly polluted to start with, since its source is mainly sewerage and waste water. I think the only think that could help is detailed data about the pollution of each river, which is not available. Keeping in mind that this is just a small part, more like an introduction to a small project (master thesis) I think am content with what I have.  Kudos again @Daniel Amrine for his help! Cheers! /Theo ... View more

Thank you very much! As I said - these were very valid points you raised! ... View more

Hi Ian, Thank you, these are valid points you raise! Of course it is really difficult to establish causalities - this is also not what I intend to show with the map. The reaons for the specific patterns of segregation in Nairobi are of course multi-causal and have to do not only with topography, but also with colonial dominance, climate, wind directions and probably much more. For my purpose it is rather about the effect of these physical patterns and how they reproduces the power strucutures that helped forming them in the first place. Due to the downstream location of many slums people face environmental hazards caused by the polution that also translate into financial pressure (cost for medicine, unpaid inability to work, etc.). The correlation between "age" of the river and pollution levels will be established by other studies I did not include in the map. Cheers! /Theo ... View more

Hi Dan! Awesome, thank you very much! I proxy the wealth of an area by average apartment prices for each neighborhood, because this data is most easily available and, I guess, rather robust. Your suggestion looks very interesting indeed - this is exactly what I was looking for! I'll try to implement it this week and will post any progress here, in case others have a similar problem. I like the idea with the distance raster. maybe I try to create one not from the source of each river (because these are quite hard to locate) but maybe (to keep things simple) originating from the city boundary. Before the rivers enter Nairobi the environment is mostly rather natural and I don't expect much pollution before they enter settled areas. But I'll think about that... Thank you very much, this is really, really helpful! /Theo ... View more