is{row,column,matrix} are builtin functions, not M-files

src/initialize_dseries_class.m

@@ -112,15 +112,15 @@ if ~exist('one_sided_hp_filter','file')
     p{end+1} = 'utilities/missing/one_sided_hp_filter';
 end
 
-if ~exist('OCTAVE_VERSION') && ~exist('ismatrix','file')
+if ~exist('OCTAVE_VERSION') && ~exist('ismatrix','builtin')
     p{end+1} = 'utilities/missing/ismatrix';
 end
 
-if ~exist('OCTAVE_VERSION') && ~exist('isrow','file')
+if ~exist('OCTAVE_VERSION') && ~exist('isrow','builtin')
     p{end+1} = 'utilities/missing/isrow';
 end
 
-if ~exist('OCTAVE_VERSION') && ~exist('iscolumn','file')
+if ~exist('OCTAVE_VERSION') && ~exist('iscolumn','builtin')
     p{end+1} = 'utilities/missing/iscolumn';
 end