Silly spatial calc

distance.py

import math

def point_to_point(point1, point2):
    """ Distance between two points
    
    Parameters
    ----------
    point1, point2 : tuples (len = 2) of floats
        Tuples of x/y pairs defining each point.
        
    Returns
    -------
    dist : float
        The absolute distance between the points
    
    """
    
    x1, y1 = point1
    x2, y2 = point2
    return math.sqrt((y2 - y1)**2 + (x2 - x1)**2)


def point_to_line(linepoint1, linepoint2, point):
    """ Shortest distance from line defined by two points
    to a third point.
    
    Parameters
    ----------
    linepoint1, linepoint2 : tuples (len = 2) of floats
        Tuples of x/y pairs defining each end point of the line.
    point : tuple (len = 2) of floats
        Third x/y pair defining the point to which the distance
        will be determined.
    
        
    Returns
    -------
    dist : float
        The absolute distance from the line segment to the point
    
    """
    
    x1, y1 = linepoint1
    x2, y2 = linepoint2
    xp, yp = point
    
    top = (y2 - y1)*xp - (x2 - x1)*yp + x2*y1 - y2*x1
    line_dist = point_to_point(linepoint1, linepoint2)
    return math.abs(top) / line_dist


def _prep_pline(polyline):
    return polyline, polyline[1:] + polyline[1:]


def point_to_polygon(polygon, point):
    polygon1, polygon2 = _prep_pline(polygon)
    distances = []
    for linepoint1, linepoint2 in zip(polygon1, polygon2):
        d = point_to_line(linepoint1, linepoint2, point)
        distances.append(d)
        
    index = np.argmin(d)
    return distances[index], polygon1[index], polygon2[index]