added swap method to touchstone

NanoVNASaver/Touchstone.py

@@ -149,9 +149,8 @@ class Touchstone:
                          float(self._interp[name]["real"](freq)),
                          float(self._interp[name]["imag"](freq)))
 
-    def s_swap(self):
-        for idx, s11, s21, s12, s22 in enumerate(self.sdata):
-            self.sdata[idx] = s22, s12, s21, s11
+    def swap(self):
+        self.sdata = [self.s22, self.s12, self.s21, self.s11]
 
     def min_freq(self) -> int:
         return self.s("11")[0].freq

test/test_touchstone.py

@@ -107,6 +107,14 @@ class TestTouchstoneTouchstone(unittest.TestCase):
             ts.load()
         self.assertRegex(cm.output[0], "No such file or directory")
 
+    def test_swap(self):
+        ts = Touchstone("./test/data/valid.s2p")
+        ts.load()
+        s11, s21, s12, s22 = ts.sdata
+        ts.swap()
+        s11_, s21_, s12_, s22_ = ts.sdata
+        self.assertEqual([s11_, s21_, s12_, s22_] ,[s22, s12, s21, s11])
+
     def test_db_conversation(self):
         ts_db = Touchstone("./test/data/attenuator-0643_DB.s2p")
         ts_db.load()