fix index problem in smoothing dialog

src/gui_qt/math/smooth.py

@@ -12,10 +12,10 @@ class QSmooth(QtWidgets.QDialog, Ui_SmoothDialog):
 
     @QtCore.pyqtSlot(int, name='on_comboBox_currentIndexChanged')
     def change_mode(self, idx: int):
-        if idx == 2:
+        if idx == 1:
             self.widget.show()
             self.widget_2.hide()
-        elif idx == 3:
+        elif idx == 2:
             self.widget.show()
             self.widget_2.show()
         else:
@@ -29,12 +29,24 @@ class QSmooth(QtWidgets.QDialog, Ui_SmoothDialog):
         idx = self.comboBox.currentIndex()
 
         # this order must match the combobox
-        para['mode'] = ['mean', 'savgol', 'loess', 'median', 'std', 'var', 'max', 'min', 'sum'][idx]
+        para['mode'] = [
+            'mean',
+            'savgol',
+            'loess',
+            'median',
+            'std',
+            'var',
+            'max',
+            'min',
+            'sum',
+        ][idx]
 
-        if idx == 2:
+        # Savitzky-Golay needs also polynomial degree
+        if idx == 1:
             para['deg'] = self.polynom_spinBox.value()
 
-        if idx == 3:
+        # LOESS needs also polynomial degree and number of iterations
+        if idx == 2:
             para['deg'] = self.polynom_spinBox.value()
             para['it'] = self.iter_spinBox.value()