python - Removing points inside several polygons -

the data: have co-ordinates of 2 variables a , b of length 100,000 each , have text file containing co-ordinates of several polygons.

i remove points of , b inside different polygons.

to so, trying use the code answer in stackoverflow 1 point , 1 polygon.

the method have chalked out go problem several points , several polygons this:

• take co-ordinates of first polygon
• run function 100,000 points of a , b , if inside, append them list, can use later compare original , b
• perform above 2 steps co-ordinates of second polygon , on...

now have 2 problems facing me, don't know how proceed with.

1. the text file containing co-ordinates of polygons looks this:

   020241-041200 4 30.83 -3.69 30.82 -3.69 30.82 -3.73 30.83 -3.73

   020241-041200 12 30.91 -4.03 30.89 -4.03 30.85 -4.05 30.83 -4.07 30.82 -4.09 30.84 -4.16 30.89 -4.19 30.96 -4.16 30.97 -4.13 30.97 -4.08 30.95 -4.05 30.93 -4.04

   here (020241-041200) id of polygon, , (4) number of corners polygon has, 30.83 x co-ordinate of first corner , -3.69 y co-ordinate of first corner , on.

   i want skip first 2 columns can consider x,y co-ordinates of polygons. how do that?

2. the polygons not of same shape, can see, the second polygon has 12 corners compared 4 in first one.

the 100,000 points of a , b

if there convenient way, other solution have given above, useful.

all want are, points of , b outside polygons.

when "those points of , b outside polygons" mean outside all of polygons or outside any of polygons?

here is:

1. a routine read in polygon points , create appropriate data structure use point_in_poly function.
2. a routine check if point in of polygons.

here routine read polygon points file:

def readpolygons(path):   polygons = []   open(path) f:     line in f:                                         # (1)       words = [ float(y) y in (line.split())[2:] ]     # (2)       poly = zip (words[::2], words[1::2])                 # (3)       if len(poly):                                        # (4)         polygons.append(poly)   return polygons 

each polygon represented list of pairs of floats, , routine returns list of polygons.

notes:

1. iterate on of lines in file.
2. split line words, drop first 2 words [2:] , convert each word float.
3. create list of pairs, taking 1st, 3rd, 5th, etc x coordinates , 2nd, 4th, 6th, etc y coordinates.
4. ignore blank lines.

here routine check if point in polygon:

def inanypolygon(x,y,polygons):   p in polygons:     if point_in_poly(x,y,p):       return true   return false 

if criteria "in polygons", use:

def inallpolygons(x,y,polygons):   p in polygons:     if not point_in_poly(x,y,p):       return false   return true 

update: if have list of points points, can create list containing points not in of polygons with:

outliers = [] p in points:   (x,y) = p   if not inanypolygons(x,y,polygons):     outliers.append(p) return outliers 

if a , b lists of numbers representing x , y coordinates respectively of 100000 points, here code find outliers:

outliers = [] (x,y) in zip(a,b):   if not inanypolygons(x,y,polygons):     outliers.append((x,y)) return outliers