Updates plot model in OhmPiHardware

ohmpi/hardware_system.py

@@ -316,13 +316,17 @@ class OhmPiHardware:
 
     def _plot_readings(self, save_fig=False):
         # Plot graphs
-        fig, ax = plt.subplots(nrows=3, sharex=True)
+        fig, ax = plt.subplots(nrows=4, sharex=True)
         ax[0].plot(self.readings[:, 0], self.readings[:, 3], '-r', marker='.', label='iab')
         ax[0].set_ylabel('Iab [mA]')
         ax[1].plot(self.readings[:, 0], self.readings[:, 2] * self.readings[:, 4], '-b', marker='.', label='vmn')
         ax[1].set_ylabel('Vmn [mV]')
         ax[2].plot(self.readings[:, 0], self.readings[:, 2], '-g', marker='.', label='polarity')
         ax[2].set_ylabel('polarity [-]')
+        v = self.readings[:, 2] != 0
+        ax[3].plot(self.readings[:, 0], (self.readings[v, 2] * self.readings[v, 4] - self.sp) / self.readings[v, 3],
+                   '-m', marker='.', label='polarity')
+        ax[3].set_ylabel('R [ohm]')
         fig.legend()
         if save_fig:
             fig.savefig(f'figures/test.png')