6 ms·

You could probably do the same in Canada fwiw.

by rapind 10y ago

Retric 10y ago
True enough. Though Canada has more land than China and less than 3% of China's population. So, it's not nearly as big a deal.
tossaway1 10y ago
Technically you could draw such a straight line in any country.
- 0xffff2 10y ago
  You could draw a straight line across any country that divides the population into 6%/94%, but I doubt there are many countries where the 94% side would be smaller than the 6% side for any line.
- dxbydt 10y ago
  This is such an interesting idea! Lots of potential. Given n (city,population, area) tuples for country C, find 2 cities, the line thru which slices C into two land masses M and N. M would then have k tuples and N would have n-k, such that the ratio of aggregate population of k tuples to the aggregate population of n-k would be 90+delta:10-delta, for delta in interval [1,9], whilst simultaneously you have the ratio of the aggregate area of the k tuples to the aggregate area of n-k working out to 1+nabla:1-nabla, for nabla in [0,0.5]. No idea what the optimal algorithm would be, short of brute force so O(n^2). This is the sort of DS project a HuffPo would run - you can slice up countries not just based on 94:6 population but also crime rate, education, victims of homicide, what have you; all you need in tuples with larger arity.
  - ethbro 10y ago
    Given the city-local nature of most population density, I'd imagine a grow-out-from-cities + line fit model would work fairly well at lower computational complexity. It'd be curious what different countries look like in terms of gradient decent difficulty on population density. I'd imagine most look fairly similar (densely populated regional urban areas surrounded by rural), but I imagine there are exceptions to some degree out there?
  - Retric 10y ago
    There are not that many city's in any given country so N^2 is probably not a big deal. However, you can get approximate results by drawing a line at every angle through a country and then moving that line up and down. Then just look for city's near any good candidate lines.
    - dxbydt 10y ago
      > drawing a line at every angle through a country and then moving that line up and down. This part is quite messy. For every given (c1,c2) city pair, you'd get 1 straight line that connects c1 to c2. Then for every city ck, you need info on whether ck is above that line or below - you can compute that by point-slope geometry with the lat-long coordinates ( given point p(x,y) & line l with some slope, is p above l or below ). If you want to poke around, the dataset is here: http://seer.cancer.gov/popdata/ http://seer.cancer.gov/popdata/
  - theoh 10y ago
    "tuples with larger arity" is just computer scientist speak for "take more things into account". Given the generality and popularity of sweepline algorithms in computational geometry, I'm wondering where the problem is here. Can't you just move a sweepline across a given territory in any direction and get a result? If you want maximum outrage (largest value of X in smallest area), I agree that's more complex and I'm not sure how you would prove an optimum result.
- maerF0x0 10y ago
  But you couldnt draw a straight line that has half the land area on each side yet 94/6% split of population.
- waterhouse 10y ago
  Consider a country with utterly uniform population density. It is trivially false that you can draw "a straight line with 6% of the population on the larger half, and 94% of the population on the smaller half" in such a country. I would be very surprised if all countries in the world were far enough from "uniform population density" for your statement to apply to them.
Noseshine 10y ago
Is it really uninhabitable? The territories in the north maybe too harsh, but with global warming helping too I think the southern half is quite alright, which is huge. It's all forest, lots of lakes, no lack of water and not too high, and no desert.
- Retric 10y ago
  On the western half: The 'low' areas have minimal rainfall and are 1KM over sea level. http://www.chinamaps.org/china/china-map-of-precipitation-annual.html http://www.chinamaps.org/china/china-map-of-precipitation-an... The high areas get a little more rainfall, but are mostly 4-5+km over sea level. http://www.china-food-security.org/data/maps/dem/dem_h.htm http://www.china-food-security.org/data/maps/dem/dem_h.htm Combine them and you can see why the population map looks the way it does. http://www.china-mike.com/china-travel-tips/tourist-maps/china-population-maps/ http://www.china-mike.com/china-travel-tips/tourist-maps/chi...
  - Noseshine 10y ago
    Uhm... Canada, not China. I responded to the comment that said > You could probably do the same in Canada fwiw. I would not ask about China, I've seen enough documentaries about their deserts and high plateaus. Some of them about the silk road, which was not an easy one because of that geography.
    - soundwave106 10y ago
      From what I see, there's a pretty good correlation between the population density map (https://www.britannica.com/place/Canada/images-videos/Population-density-of-Canada/71476 https://www.britannica.com/place/Canada/images-videos/Popula...) and the portion of Canada at least sporadically covered by permafrost. (http://www.enr.gov.nt.ca/state-environment/13-permafrost http://www.enr.gov.nt.ca/state-environment/13-permafrost) In addition to the rather obvious climate this implies (eg, rather cold), from what I understand, building anything on permafrost is very challenging.
frandroid 10y ago
Canada and China are roughly the same size.

You could probably do the same in Canada fwiw.

by rapind 10y ago

You could probably do the same in Canada fwiw.

True enough. Though Canada has more land than China and less than 3% of China's population. So, it's not nearly as big a deal.

tossaway1 10y ago

Technically you could draw such a straight line in any country.

0xffff2 10y ago
You could draw a straight line across any country that divides the population into 6%/94%, but I doubt there are many countries where the 94% side would be smaller than the 6% side for any line.
dxbydt 10y ago
This is such an interesting idea! Lots of potential. Given n (city,population, area) tuples for country C, find 2 cities, the line thru which slices C into two land masses M and N. M would then have k tuples and N would have n-k, such that the ratio of aggregate population of k tuples to the aggregate population of n-k would be 90+delta:10-delta, for delta in interval [1,9], whilst simultaneously you have the ratio of the aggregate area of the k tuples to the aggregate area of n-k working out to 1+nabla:1-nabla, for nabla in [0,0.5]. No idea what the optimal algorithm would be, short of brute force so O(n^2). This is the sort of DS project a HuffPo would run - you can slice up countries not just based on 94:6 population but also crime rate, education, victims of homicide, what have you; all you need in tuples with larger arity.
- ethbro 10y ago
  Given the city-local nature of most population density, I'd imagine a grow-out-from-cities + line fit model would work fairly well at lower computational complexity. It'd be curious what different countries look like in terms of gradient decent difficulty on population density. I'd imagine most look fairly similar (densely populated regional urban areas surrounded by rural), but I imagine there are exceptions to some degree out there?
- Retric 10y ago
  There are not that many city's in any given country so N^2 is probably not a big deal. However, you can get approximate results by drawing a line at every angle through a country and then moving that line up and down. Then just look for city's near any good candidate lines.
  - dxbydt 10y ago
    > drawing a line at every angle through a country and then moving that line up and down. This part is quite messy. For every given (c1,c2) city pair, you'd get 1 straight line that connects c1 to c2. Then for every city ck, you need info on whether ck is above that line or below - you can compute that by point-slope geometry with the lat-long coordinates ( given point p(x,y) & line l with some slope, is p above l or below ). If you want to poke around, the dataset is here: http://seer.cancer.gov/popdata/ http://seer.cancer.gov/popdata/
- theoh 10y ago
  "tuples with larger arity" is just computer scientist speak for "take more things into account". Given the generality and popularity of sweepline algorithms in computational geometry, I'm wondering where the problem is here. Can't you just move a sweepline across a given territory in any direction and get a result? If you want maximum outrage (largest value of X in smallest area), I agree that's more complex and I'm not sure how you would prove an optimum result.
maerF0x0 10y ago
But you couldnt draw a straight line that has half the land area on each side yet 94/6% split of population.
waterhouse 10y ago
Consider a country with utterly uniform population density. It is trivially false that you can draw "a straight line with 6% of the population on the larger half, and 94% of the population on the smaller half" in such a country. I would be very surprised if all countries in the world were far enough from "uniform population density" for your statement to apply to them.

Noseshine 10y ago

Is it really uninhabitable? The territories in the north maybe too harsh, but with global warming helping too I think the southern half is quite alright, which is huge. It's all forest, lots of lakes, no lack of water and not too high, and no desert.

Retric 10y ago
On the western half: The 'low' areas have minimal rainfall and are 1KM over sea level. http://www.chinamaps.org/china/china-map-of-precipitation-annual.html http://www.chinamaps.org/china/china-map-of-precipitation-an... The high areas get a little more rainfall, but are mostly 4-5+km over sea level. http://www.china-food-security.org/data/maps/dem/dem_h.htm http://www.china-food-security.org/data/maps/dem/dem_h.htm Combine them and you can see why the population map looks the way it does. http://www.china-mike.com/china-travel-tips/tourist-maps/china-population-maps/ http://www.china-mike.com/china-travel-tips/tourist-maps/chi...
- Noseshine 10y ago
  Uhm... Canada, not China. I responded to the comment that said > You could probably do the same in Canada fwiw. I would not ask about China, I've seen enough documentaries about their deserts and high plateaus. Some of them about the silk road, which was not an easy one because of that geography.
  - soundwave106 10y ago
    From what I see, there's a pretty good correlation between the population density map (https://www.britannica.com/place/Canada/images-videos/Population-density-of-Canada/71476 https://www.britannica.com/place/Canada/images-videos/Popula...) and the portion of Canada at least sporadically covered by permafrost. (http://www.enr.gov.nt.ca/state-environment/13-permafrost http://www.enr.gov.nt.ca/state-environment/13-permafrost) In addition to the rather obvious climate this implies (eg, rather cold), from what I understand, building anything on permafrost is very challenging.

frandroid 10y ago

Canada and China are roughly the same size.