t_fnet(arr_c = -3)  # arr_c = -1 to -3: points at both ends</span></span></span>
<span class="r-in"><span><span class="co"># plot_fnet(arr_c = -2)  # point at far end</span></span></span>
<span class="r-in"><span><span class="fu">plot_fnet</span><span class="op">(</span>arr_c <span class="op">=</span> <span class="op">+</span><span class="fl">2</span><span class="op">)</span>    <span class="co"># crr_c = 1-3: V-shape arrows at far end</span></span></span>
<span class="r-plt img"><img src="plot_fnet-23.png"