Update 4_sommerfeld_model.md

src/4_sommerfeld_model.md

@@ -54,7 +54,7 @@ ax.set_ylim(0.0, 11);
 ax.set_xlabel(r"$k \quad \left[ \frac{2 \pi}{L} \right]$");
 ax.set_ylabel(r"$\varepsilon$");
 
-ax.set_xticklabels([""] + ks + [""]);
+ax.set_xticklabels([""] + ks.tolist() + [""]);
 ax.set_yticks([]);
 
 draw_classic_axes(ax, xlabeloffset=.6);