-4	<--- lowest x-value to plot slopes for
4	<--- highest x-value to plot slopes for
-3	<--- lowest y-value to plot slopes for
3	<--- highest y-value to plot slopes for
50	<--- number of slopes in the x-direction to plot
50	<--- number of slopes in the y-direction to plot
0	<--- 0 to make all the slopes the same length, 1 to scale them 
0.5	<--- relative size of the slopes