Added test case and function to support NaN

Author: taytzehao

doc/source/whatsnew/v1.3.0.rst

@@ -874,7 +874,7 @@ Sparse
 
 - Bug in :meth:`DataFrame.sparse.to_coo` raising ``KeyError`` with columns that are a numeric :class:`Index` without a 0 (:issue:`18414`)
 - Bug in :meth:`SparseArray.astype` with ``copy=False`` producing incorrect results when going from integer dtype to floating dtype (:issue:`34456`)
-- Bug in :meth:`max` and `min` for SparseArrat type do not exist (:issue:`40921`)
+- Bug in :meth:`max` and `min` for :class:`SparseArray` type do not exist (:issue:`40921`)
 
 ExtensionArray
 ^^^^^^^^^^^^^^

pandas/core/arrays/sparse/array.py

@@ -1392,20 +1392,26 @@ def mean(self, axis=0, *args, **kwargs):
             nsparse = self.sp_index.ngaps
             return (sp_sum + self.fill_value * nsparse) / (ct + nsparse)
 
-
     def max(self, axis=0, *args, **kwargs):
         nv.validate_max(args, kwargs)
 
         if self.sp_index.ngaps > 0 and np.all(self._valid_sp_values < 0):
+            
+            if self.size>0 and self._valid_sp_values.size==0:
+                return np.nan
+                
             return 0
         else:
             return np.amax(self._valid_sp_values, axis)
 
-
     def min(self, axis=0, *args, **kwargs):
         nv.validate_min(args, kwargs)
 
         if self.sp_index.ngaps > 0 and np.all(self._valid_sp_values > 0):
+            
+            if self.size>0 and self._valid_sp_values.size==0:
+                return np.nan
+            
             return 0
         else:
             return np.amin(self._valid_sp_values, axis)