11870.com hotels density map in Madrid

CartoDB code

SELECT count(cartodb_id) as ct, ST_Transform(ST_Buffer(ST_SnapToGrid(the_geom,0.002),0.001, ‘quad_segs=2 endcap=square’),3857) as the_geom_webmercator FROM hoteles_playground GROUP BY ST_SnapToGrid(the_geom,0.002)

#hoteles_playground{
  polygon-fill:#FF6600;
  polygon-opacity:.7;
  }
#hoteles_playground[ct<=40]{
  polygon-fill:#BD0026}
#hoteles_playground[ct<=20]{
  polygon-fill:#F03B20}
#hoteles_playground[ct<=13]{
  polygon-fill:#FD8D3C}
#hoteles_playground[ct<=7]{
  polygon-fill:#FEB24C}
#hoteles_playground[ct<=3]{
  polygon-fill:#FED976}
#hoteles_playground[ct<=2]{
  polygon-fill:#FFFFB2
}

This is a fun bit of SQL, thanks! One does have to replace the smart quotes around quad_segs=2 endcap=square before the query will run, however.

Plus, this snippet works somewhat on (multi)linestrings, depending on your data's density and the styling you apply. It does run a bit slowly the first time through, depending on your radii/etc, but I suppose that could also just be a limitation of the free hosted CartoDB (which is awesome, by the way). Here's what I ended up with after some fiddling:

SELECT count(cartodb_id) as ct, ST_Transform(ST_Buffer(ST_SnapToGrid(the_geom,0.04),0.02, 'endcap=square quad_segs=4'),3857) as the_geom_webmercator FROM testing GROUP BY ST_SnapToGrid(the_geom,0.04)

... which can be seen in action here: http://bit.ly/GAVaB4

Hey! That's cool! :)