将坐标列表排序成条状

Question

I am reading in lat and long coordinates from a csv file. My goal is to take the coordinates and sort them into their respective stips as a list of lists ie [[strip 1 coordiantes],[strip 2 coordiantes],[strip 3 coordinates]]

The ultimate goal is to use these strips to identify the outer most corner waypoints to be used for other work. Simply getting standard max, min x and y of all coordinates doesn't work as the orientation of the points is not fixed.

Go from this:

[['41.55275997', '21.97765353'], ['41.55273016', '21.97763498'], ['41.55270034', '21.97761643'], ['41.55267052', '21.97759788'], ['41.55264071', '21.97757933'], ['41.55270455', '21.97740142'], ['41.55273436', '21.97741997'], ['41.55276418', '21.97743852'], ['41.55279399', '21.97745707'], ['41.55282381', '21.97747562'], ['41.55275997', '21.97765353'], ['41.55273016', '21.97763498'], ['41.55270034', '21.97761643'], ['41.55267052', '21.97759788'], ['41.55264071', '21.97757933']]

To this:

[[['41.55275997', '21.97765353'], ['41.55273016', '21.97763498'], ['41.55270034', '21.97761643'], ['41.55267052', '21.97759788'], ['41.55264071', '21.97757933']], [['41.55270455', '21.97740142'], ['41.55273436', '21.97741997'], ['41.55276418', '21.97743852'], ['41.55279399', '21.97745707'], ['41.55282381', '21.97747562']], [['41.55275997', '21.97765353'], ['41.55273016', '21.97763498'], ['41.55270034', '21.97761643'], ['41.55267052', '21.97759788'], ['41.55264071', '21.97757933']]]

My plan was to use rise/run calculation between the points. However as the points slope changes as the coordinate moves to another strip and again when comparing points on same strip I am unsure how to proceed.

Curr Code:

# get waypoint coordiantes
coordinateList = []
csv_file.seek(0)
next(csv_reader)
#add all coordinates in csv to a single list
for line in csv_reader:
    coordinateList.append([line[0],line[1]])
print(coordinateList)

#Take coordinate list (list of lists) and add coordinates to lists reprenting a s ingle stip

#Get the rise over run from the first two coordinates.
rise = float(coordinateList[0][1]) - float(coordinateList[1][1])
run = float(coordinateList[0][0]) - float(coordinateList[1][0])
print(rise,run)
#add first two coordiantes to a strip
coordStips = [[coordinateList[0],coordinateList[1]]]

#iterate through remaining coordiantes and compare
for coord1,coord2 in zip(coordinateList[1:-1:], coordinateList[2::]):
    #print(coord1,coord2)
    rise = float(coord2[1]) - float(coord1[1])
    run = float(coord2[0]) - float(coord1[0])
    print(rise,run)

Any help is appreciated.

EDIT: Here is the slopes that I have currently calculated. Not sure why they are all slightly different.

0.622065727665411
0.622065727665411
0.6222744045453561
-2.7868107768422306
0.6222744045453561
0.6220657278136351
0.6222744045453561
0.622065727665411
-2.7868107768422306
0.6222744046936797
0.622065727665411
0.622065727665411
0.6222744045453561

Solution:

# get waypoint coordiantes
        coordinateList = []
        csv_file.seek(0)
        next(csv_reader)
        #add all coordinates in csv to a single list
        for line in csv_reader:
            coordinateList.append([line[0],line[1]])
        print(coordinateList)

        #Take coordinate list (list of lists) and add coordinates to lists reprenting a s ingle stip

        #Get the rise over run from the first two coordinates.
        rise = float(coordinateList[0][1]) - float(coordinateList[1][1])
        run = float(coordinateList[0][0]) - float(coordinateList[1][0])
        masterslope = rise/run

        #---Strip List set Up
        #add first two coordiantes to a strip
        coordStrips = [[coordinateList[0],coordinateList[1]]]
        stripCount = 0
        switch = False


        #----------Iteration
        #iterate through remaining coordiantes and compare
        for coord1,coord2 in zip(coordinateList[1:-1:], coordinateList[2::]):
            #if previous waypoint was found to be on a new strip
            if switch == True:
                coordStrips[stripCount].append(coord2)

                rise = float(coord2[1]) - float(coord1[1])
                run = float(coord2[0]) - float(coord1[0])
                masterslope = rise/run

                switch = False
                continue
            #print(coord1,coord2)
            rise = float(coord2[1]) - float(coord1[1])
            run = float(coord2[0]) - float(coord1[0])
            slope = rise/run
            diff = abs(masterslope-slope)
            #they are in the same strip, add to current strip
            if diff < 0.5:
                coordStrips[stripCount].append(coord2)
            #new strip
            else:

                stripCount+= 1
                coordStrips.append([coord2])
                switch = True

Answer 1

I think you are on the right track. Assuming that points that belong to one "strip" are already together in the list, you just have to remember the slope of the current group and keep adding points while their slope wrt the last point is (roughly) the same as the last slope.

points = [tuple(map(float, t)) for t in coordinateList]

x2, y2 = points[0]
groups = [[(x2, y2)]]
slope = None
close = lambda a, b: abs(a - b) < epsilon

for x, y in points[1:]:
    if slope is None or close(x-x2, slope[0]) and close(y-y2, slope[1]):
        groups[-1].append((x,y))
        slope = (x-x2, y-y2)
    else:
        groups.append([(x,y)])
        slope = None
    x2, y2 = x, y

The tricky part is when to consider the slopes "close enough". For your example, any epsilon from 1e-4 to 1e-7 seems to work, resulting in the groups

[(41.55275997, 21.97765353), (41.55273016, 21.97763498), (41.55270034, 21.97761643), (41.55267052, 21.97759788), (41.55264071, 21.97757933)]
[(41.55270455, 21.97740142), (41.55273436, 21.97741997), (41.55276418, 21.97743852), (41.55279399, 21.97745707), (41.55282381, 21.97747562)]
[(41.55275997, 21.97765353), (41.55273016, 21.97763498), (41.55270034, 21.97761643), (41.55267052, 21.97759788), (41.55264071, 21.97757933)]