save previews in graphics

src/gui_qt/fit/fitwindow.py

@@ -413,7 +413,15 @@ class QFitDialog(QtWidgets.QWidget, Ui_FitDialog):
             parameters = model['parameter']
             color = model['color']
 
+            seen_parameter = []
+
             for p, kwargs in parameters.values():
+                if (p, kwargs) in seen_parameter:
+                    # plot only previews with different parameter
+                    continue
+
+                seen_parameter.append((p, kwargs))
+
                 if is_complex is not None:
                     y = f.func(x, *p, complex_mode=is_complex, **kwargs)
                     if np.iscomplexobj(y):