Changes the way sp is taken into account in R computation within ohmpi

ohmpi/hardware_system.py

@@ -220,7 +220,7 @@ class OhmPiHardware:
             return np.nan
 
     @property
-    def sp(self):  # TODO: use a time window within pulses
+    def sp(self):  # TODO: allow for different strategies for computing sp (i.e. when sp drift is not linear)
         if self.readings.shape == (0,) or len(self.readings[self.readings[:, 2] == 1, :]) < 1 or \
                 len(self.readings[self.readings[:, 2] == -1, :]) < 1:
             self.exec_logger.warning('Unable to compute sp: readings should at least contain one positive and one '

ohmpi/ohmpi.py

@@ -460,8 +460,8 @@ class OhmPi(object):
                 delay = 0.
             x = np.where((self._hw.readings[:, 0] >= delay) & (self._hw.readings[:, 2] != 0))
             print(f'length of series: {len(x)}')
-            R = np.mean((self._hw.readings[x, 2] * self._hw.readings[x, 4] - self._hw.sp) / self._hw.readings[x, 3])
-            R_std = 100. * np.std((self._hw.readings[x, 2] * self._hw.readings[x, 4] - self._hw.sp) / self._hw.readings[x, 3]) / R
+            R = np.mean((self._hw.readings[x, 2] * (self._hw.readings[x, 4] - self._hw.sp)) / self._hw.readings[x, 3])
+            R_std = 100. * np.std((self._hw.readings[x, 2] * (self._hw.readings[x, 4] - self._hw.sp)) / self._hw.readings[x, 3]) / R
             d = {
                 "time": datetime.now().isoformat(),
                 "A": quad[0],