fix the plot label

src/2_debye_model.md

@@ -68,10 +68,10 @@ fit = curve_fit(c_einstein, T, c, 500)
 T_E = fit[0][0]
 
 fig, ax = pyplot.subplots()
-ax.scatter(T, c)
+ax.scatter(T, c, label='Silver')
 ax.plot(temp, c_einstein(temp, T_E), label=f'Einstein model, $T_E={T_E:.5}K$')
 ax.text(T_E+3, 1.5, r'$T=T_E$', ha='left', color='r');
-ax.plot([T_E, T_E], [0, 3], 'r--', label = 'Silver')
+ax.plot([T_E, T_E], [0, 3], 'r--')
 ax.set_ylim(bottom=0, top=3)
 ax.set_xlim(0, 215)
 ax.set_xlabel('$T(K)$')