feature: add frequency_at_index method to GenericSpectrogram (#129).

changelog/172.feature.rst

@@ -0,0 +1 @@
+Added frequency_at_index method to GenericSpectrogram class

radiospectra/spectrogram/spectrogrambase.py

@@ -107,3 +107,13 @@ def __repr__(self):
             f" {self.wavelength.min} - {self.wavelength.max},"
             f" {self.start_time.isot} to {self.end_time.isot}>"
         )
+
+    def frequency_at_index(self, index):
+        """
+        Returns the frequency at a specific index.
+        """
+        freq = self.frequencies
+        max_freq = len(freq)
+        if index < 0 or index >= max_freq:
+            raise IndexError(f"Index {index} out of range for frequency axis with size {max_freq}.")
+        return freq[index]