[inequality] Take writeable copy before rd.shuffle (pandas 3.0)

pandas 3.0 returns a read-only array from np.asarray() of a Series (Copy-on-Write), so rd.shuffle(y) raised "ValueError: assignment destination is read-only" during the anaconda=2026.06 build. Take a writeable .copy() before the in-place shuffle. See #775.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Author: mmcky

lectures/inequality.md

@@ -284,7 +284,8 @@ for var in varlist:
         # Repeat the observations according to their weights
         counts = list(round(df[df['year'] == year]['weights'] ))
         y = df[df['year'] == year][var].repeat(counts)
-        y = np.asarray(y)
+        # `.copy()` gives a writeable array (pandas 3.0 returns a read-only one)
+        y = np.asarray(y).copy()
 
         # Shuffle the sequence to improve the plot
         rd.shuffle(y)