Use to_numpy() to convert pd.Series to np.array

The .values method isn't recommended anymore for pandas 1.0, see https://pandas.pydata.org/pandas-docs/stable/reference/api/pandas.Series.values.html#pandas.Series.values. Using to_numpy() instead.

Author: weiji14

pygmt/clib/conversion.py

@@ -241,7 +241,7 @@ def _as_array(vector):
 
     """
     if isinstance(vector, pandas.Series):
-        return vector.values
+        return vector.to_numpy()
     return np.asarray(vector)