// Take the list of station locations and fold them into the regions of a grid.
func BuildGrid(locs []*StationLoc, zips []*Zip, r image.Rectangle, c *GridConfig) *Grid {
nx, ny := c.W, c.H
regs := make([][]*Region, nx)
for i := 0; i < nx; i++ {
regs[i] = make([]*Region, ny)
}
// create all active rectangles
for _, xy := range c.Active {
i, j := xy[0], xy[1]
regs[i][j] = &Region{
I: i,
J: j,
Rect: image.Rect(i*c.Size, j*c.Size, (i+1)*c.Size, (j+1)*c.Size),
}
}
// assign stations to their region
for _, loc := range locs {
ix, iy := int(loc.X/float64(c.Size)), int(loc.Y/float64(c.Size))
r := regs[ix][iy]
if r == nil {
continue
}
r.Stations = append(r.Stations, loc)
}
// assign zips to their region
for _, zip := range zips {
ix, iy := int(zip.X/float64(c.Size)), int(zip.Y/float64(c.Size))
if ix >= c.W || ix < 0 || iy >= c.H || iy < 0 {
continue
}
r := regs[ix][iy]
if r == nil {
continue
}
r.Zips = append(r.Zips, zip)
}
grid := &Grid{
W: nx,
H: ny,
Grid: regs,
}
for _, xy := range c.Active {
i, j := xy[0], xy[1]
regs[i][j].Nearest = NearestN(c, grid, regs[i][j], 20)
city := LabelFor(grid, i, j)
regs[i][j].City = city
}
return grid
}