Extract points in a defined direction and distance

'directionaldist' extract points in 'pk' that are in a direction relative
to reference point 'p' (Output: 'ind'). You can define distance interval
with 'r1' and 'r2', and also angle interval by 'dirAngle' and 'margin'.
It also extracts the nearest neighbor in the specified direction and
distance interval (Output: 'indMin').
Try the "demo.m" file for some illustration of the function.
Inputs
Data
'p': Reference point location 2x1
'pk': location of N points 2xN

Parameters
'r1': max distance to 'p' (Euclidean distance is used)
'r2': min distance to 'p' (Euclidean distance is used)
'dirAngle': reltaive direction angle from point 'p' to 'pk' (in degrees)
'margin': angle margin, will be used as defining the angle interval
[dirAngle+margin, dirAngle-margin]. If margin is zero, it is possible
that you will not find any points that are exactly at dirAngle direction.
So it is good to give some margin. Or it can be used for other purposes.
'dirType': direction type 'none' or 'symmetric', just try it out!

Outputs

'ind': indices of points of 'pk', which are in the direction of
[dirAngle+margin, dirAngle-margin] relative to reference point 'p',
where max distance to 'p' is 'r1', and min distance to 'p' is 'r2'.
'indMin': index of nearest neighbor point in 'pk' to 'p' in the specified
direction angle interval

Note: This function uses a function called 'nearestneighbour'
which is downloaded from fileexchange linke below:
(http://www.mathworks.com/matlabcentral/fileexchange/12574-nearestneighbour-m)

Copyright 2016 Abdullah H. Ozcan