If you have a polyline and want the slope or angle of each segment, consider the simple example:
% vertices of a polyline (this case is a closed polygon, but w/e)
x = [0 1 0.5 0];
y = [0 0 sqrt(3)/2 0];
% segment slope and angle
slope = diff(y)./diff(x)
theta = atan2d(diff(y),diff(x))
% plot it
plot(x,y)
