--- a/NEWS	Mon Aug 13 11:41:17 2018 -0700
+++ b/NEWS	Mon Aug 13 12:17:58 2018 -0700
@@ -79,6 +79,7 @@
       ---------------------|------------------
       findstr              | strfind
       flipdim              | flip
+      isdir                | isfolder or dir_in_loadpath
       isequalwithequalnans | isequaln
       isstr                | ischar
       setstr               | char

--- a/libinterp/corefcn/syscalls.cc	Mon Aug 13 11:41:17 2018 -0700
+++ b/libinterp/corefcn/syscalls.cc	Mon Aug 13 12:17:58 2018 -0700
@@ -852,7 +852,7 @@
   @result{} err = 0
   @result{} msg =
 @end example
-@seealso{lstat, ls, dir}
+@seealso{lstat, ls, dir, isfolder}
 @end deftypefn */)
 {
   if (args.length () != 1)

--- a/libinterp/corefcn/utils.cc	Mon Aug 13 11:41:17 2018 -0700
+++ b/libinterp/corefcn/utils.cc	Mon Aug 13 12:17:58 2018 -0700
@@ -840,7 +840,7 @@
        doc: /* -*- texinfo -*-
 @deftypefn {} {} is_absolute_filename (@var{file})
 Return true if @var{file} is an absolute filename.
-@seealso{is_rooted_relative_filename, make_absolute_filename, isdir}
+@seealso{is_rooted_relative_filename, make_absolute_filename, isfolder}
 @end deftypefn */)
 {
   if (args.length () != 1)
@@ -861,7 +861,7 @@
        doc: /* -*- texinfo -*-
 @deftypefn {} {} is_rooted_relative_filename (@var{file})
 Return true if @var{file} is a rooted-relative filename.
-@seealso{is_absolute_filename, make_absolute_filename, isdir}
+@seealso{is_absolute_filename, make_absolute_filename, isfolder}
 @end deftypefn */)
 {
   if (args.length () != 1)
@@ -885,7 +885,7 @@
 system.
 
 No check is done for the existence of @var{file}.
-@seealso{canonicalize_file_name, is_absolute_filename, is_rooted_relative_filename, isdir}
+@seealso{canonicalize_file_name, is_absolute_filename, is_rooted_relative_filename, isfolder}
 @end deftypefn */)
 {
   if (args.length () != 1)

--- a/scripts/gui/uigetdir.m	Mon Aug 13 11:41:17 2018 -0700
+++ b/scripts/gui/uigetdir.m	Mon Aug 13 12:17:58 2018 -0700
@@ -40,7 +40,7 @@
     error ("uigetdir: INIT_PATH and DIALOG_NAME must be string arguments");
   endif
 
-  if (! isdir (init_path))
+  if (! isfolder (init_path))
     init_path = fileparts (init_path);
   endif
 

--- a/scripts/gui/uigetfile.m	Mon Aug 13 11:41:17 2018 -0700
+++ b/scripts/gui/uigetfile.m	Mon Aug 13 12:17:58 2018 -0700
@@ -126,7 +126,7 @@
 
   if (len > 2)
     if (ischar (args{3}))
-      if (isdir (args{3}))
+      if (isfolder (args{3}))
         fdir = args{3};
         fname = fext = "";
       else

--- a/scripts/gui/uiputfile.m	Mon Aug 13 11:41:17 2018 -0700
+++ b/scripts/gui/uiputfile.m	Mon Aug 13 12:17:58 2018 -0700
@@ -90,7 +90,7 @@
 
   if (nargin > 2)
     if (ischar (varargin{3}))
-      if (isdir (varargin{3}))
+      if (isfolder (varargin{3}))
         fdir = varargin{3};
         fname = fext = "";
       else

--- a/scripts/help/which.m	Mon Aug 13 11:41:17 2018 -0700
+++ b/scripts/help/which.m	Mon Aug 13 12:17:58 2018 -0700
@@ -54,7 +54,7 @@
         endif
       else
         if (isempty (m(i).type))
-          if (isdir (m(i).file))
+          if (isfolder (m(i).file))
             printf ("'%s' is the directory %s\n",
                     m(i).name, m(i).file);
           else

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/scripts/legacy/isdir.m	Mon Aug 13 12:17:58 2018 -0700
@@ -0,0 +1,66 @@
+## Copyright (C) 2004-2018 Alois Schloegl
+##
+## This file is part of Octave.
+##
+## Octave is free software: you can redistribute it and/or modify it
+## under the terms of the GNU General Public License as published by
+## the Free Software Foundation, either version 3 of the License, or
+## (at your option) any later version.
+##
+## Octave is distributed in the hope that it will be useful, but
+## WITHOUT ANY WARRANTY; without even the implied warranty of
+## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+## GNU General Public License for more details.
+##
+## You should have received a copy of the GNU General Public License
+## along with Octave; see the file COPYING.  If not, see
+## <https://www.gnu.org/licenses/>.
+
+## -*- texinfo -*-
+## @deftypefn {} {} isdir (@var{f})
+##
+## This function is not recommended.  Use @code{isfolder} or
+## @code{file_in_loadpath} instead.
+##
+## Return true if @var{f} is a directory and false otherwise.
+##
+## Compatibility Note: The @sc{matlab} function of the same name will also
+## search for @var{f} in the load path directories.  To emulate this behavior
+## use
+## 
+## @example
+## @var{tf} = ! isempty (file_in_loadpath (@var{f}))
+## @end example
+##
+## @seealso{isfolder, file_in_loadpath, exist, stat, is_absolute_filename, is_rooted_relative_filename}
+## @end deftypefn
+
+function retval = isdir (f)
+
+  persistent warned = false;
+  if (! warned)
+    warned = true;
+    warning ("Octave:legacy-function",
+             "isdir is obsolete; use isfolder or dir_in_loadpath instead\n");
+  endif
+
+  if (nargin != 1)
+    print_usage ();
+  endif
+
+  ## Exist returns an integer but isdir should return a logical.
+  retval = (exist (f, "dir") == 7);
+
+endfunction
+
+
+## First test is necessary to provoke 1-time legacy warning
+%!test
+%! warning ("off", "Octave:legacy-function", "local");
+%! isdir (pwd ());
+
+%!assert (isdir (pwd ()))
+%!assert (! isdir (tempname ()))
+
+%!error isdir ()
+%!error isdir (1, 2)

--- a/scripts/legacy/module.mk	Mon Aug 13 11:41:17 2018 -0700
+++ b/scripts/legacy/module.mk	Mon Aug 13 12:17:58 2018 -0700
@@ -3,6 +3,7 @@
 %canon_reldir%_FCN_FILES = \
   %reldir%/findstr.m \
   %reldir%/flipdim.m \
+  %reldir%/isdir.m \
   %reldir%/isequalwithequalnans.m \
   %reldir%/isstr.m \
   %reldir%/setstr.m \

--- a/scripts/miscellaneous/copyfile.m	Mon Aug 13 11:41:17 2018 -0700
+++ b/scripts/miscellaneous/copyfile.m	Mon Aug 13 12:17:58 2018 -0700
@@ -78,7 +78,7 @@
   endif
 
   ## If f1 has more than 1 element then f2 must be a directory
-  isdir = (exist (f2, "dir") != 0);
+  isdir = isfolder (f2);
   if (numel (f1) > 1 && ! isdir)
     error ("copyfile: when copying multiple files, F2 must be a directory");
   endif

--- a/scripts/miscellaneous/isdir.m	Mon Aug 13 11:41:17 2018 -0700
+++ /dev/null	Thu Jan 01 00:00:00 1970 +0000
@@ -1,41 +0,0 @@
-## Copyright (C) 2004-2018 Alois Schloegl
-##
-## This file is part of Octave.
-##
-## Octave is free software: you can redistribute it and/or modify it
-## under the terms of the GNU General Public License as published by
-## the Free Software Foundation, either version 3 of the License, or
-## (at your option) any later version.
-##
-## Octave is distributed in the hope that it will be useful, but
-## WITHOUT ANY WARRANTY; without even the implied warranty of
-## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-## GNU General Public License for more details.
-##
-## You should have received a copy of the GNU General Public License
-## along with Octave; see the file COPYING.  If not, see
-## <https://www.gnu.org/licenses/>.
-
-## -*- texinfo -*-
-## @deftypefn {} {} isdir (@var{f})
-## Return true if @var{f} is a directory.
-## @seealso{exist, stat, is_absolute_filename, is_rooted_relative_filename}
-## @end deftypefn
-
-function retval = isdir (f)
-
-  if (nargin != 1)
-    print_usage ();
-  endif
-
-  ## Exist returns an integer but isdir should return a logical.
-  retval = (exist (f, "dir") == 7);
-
-endfunction
-
-
-%!assert (isdir (pwd ()))
-%!assert (! isdir ("this is highly unlikely to be a directory name"))
-
-%!error isdir ()
-%!error isdir (1, 2)

--- a/scripts/miscellaneous/mkdir.m	Mon Aug 13 11:41:17 2018 -0700
+++ b/scripts/miscellaneous/mkdir.m	Mon Aug 13 12:17:58 2018 -0700
@@ -71,7 +71,7 @@
 
   status = 1;
 
-  if (! isdir (parent))
+  if (! isfolder (parent))
     [grandparent, name, ext] = fileparts (parent);
     [status, msg, msgid] = mkdir_recur (grandparent, [name, ext]);
   endif
@@ -90,7 +90,7 @@
 %! unwind_protect
 %!   status = mkdir (dir);
 %!   assert (status);
-%!   assert (isdir (dir));
+%!   assert (isfolder (dir));
 %! unwind_protect_cleanup
 %!   confirm_recursive_rmdir (false, "local");
 %!   rmdir (dir1, "s");
@@ -104,7 +104,7 @@
 %!   setenv ("HOME", tmp_dir);
 %!   status = mkdir ("~/subdir");
 %!   assert (status);
-%!   assert (isdir (fullfile (tmp_dir, "subdir")));
+%!   assert (isfolder (fullfile (tmp_dir, "subdir")));
 %! unwind_protect_cleanup
 %!   rmdir (fullfile (tmp_dir, "subdir"));
 %!   rmdir (tmp_dir);

--- a/scripts/miscellaneous/module.mk	Mon Aug 13 11:41:17 2018 -0700
+++ b/scripts/miscellaneous/module.mk	Mon Aug 13 12:17:58 2018 -0700
@@ -33,7 +33,6 @@
   %reldir%/inputParser.m \
   %reldir%/inputname.m \
   %reldir%/isdeployed.m \
-  %reldir%/isdir.m \
   %reldir%/isfolder.m \
   %reldir%/ismac.m \
   %reldir%/ispc.m \

--- a/scripts/miscellaneous/movefile.m	Mon Aug 13 11:41:17 2018 -0700
+++ b/scripts/miscellaneous/movefile.m	Mon Aug 13 12:17:58 2018 -0700
@@ -87,7 +87,7 @@
   endif
 
   ## If f1 has more than 1 element f2 must be a directory
-  isdir = (exist (f2, "dir") != 0);
+  isdir = isfolder (f2);
   if (numel (f1) > 1 && ! isdir)
     error ("movefile: when moving multiple files, F2 must be a directory");
   endif

--- a/scripts/miscellaneous/tempdir.m	Mon Aug 13 11:41:17 2018 -0700
+++ b/scripts/miscellaneous/tempdir.m	Mon Aug 13 12:17:58 2018 -0700
@@ -37,7 +37,7 @@
     dirname = [dirname filesep];
   endif
 
-  if (! isdir (dirname))
+  if (! isfolder (dirname))
     warning ("tempdir: '%s' does not exist or is not a directory", dirname);
   endif
 

--- a/scripts/miscellaneous/unpack.m	Mon Aug 13 11:41:17 2018 -0700
+++ b/scripts/miscellaneous/unpack.m	Mon Aug 13 12:17:58 2018 -0700
@@ -115,7 +115,7 @@
     file = file{1};
   endif
 
-  if (isdir (file))
+  if (isfolder (file))
     if (isempty (filetype))
       error ("unpack: FILETYPE must be given for a directory");
     elseif (! any (strcmpi (filetype, "gunzip")))

--- a/scripts/miscellaneous/what.m	Mon Aug 13 11:41:17 2018 -0700
+++ b/scripts/miscellaneous/what.m	Mon Aug 13 12:17:58 2018 -0700
@@ -116,7 +116,7 @@
         w.oct{end+1} = n;
       elseif (strcmp (e, mexext ()))
         w.mex{end+1} = n;
-      elseif (n(1) == "@" && isdir (fullfile (dir, n)))
+      elseif (n(1) == "@" && isfolder (fullfile (dir, n)))
         w.classes{end+1} = n;
       endif
     endif

--- a/scripts/plot/util/private/__print_parse_opts__.m	Mon Aug 13 11:41:17 2018 -0700
+++ b/scripts/plot/util/private/__print_parse_opts__.m	Mon Aug 13 12:17:58 2018 -0700
@@ -275,7 +275,8 @@
                                           "ps", "ps2", "psc", "psc2", "pdf"})))
       have_ghostscript = ! isempty (__ghostscript_binary__ ());
       if (have_ghostscript)
-        file_exists = (numel (dir (arg_st.name)) == 1 && ! isdir (arg_st.name));
+        file_exists = (numel (dir (arg_st.name)) == 1
+                       && ! isfolder (arg_st.name));
         if (! file_exists)
           arg_st.append_to_file = false;
         endif

--- a/scripts/testfun/private/compare_plot_demos.m	Mon Aug 13 11:41:17 2018 -0700
+++ b/scripts/testfun/private/compare_plot_demos.m	Mon Aug 13 12:17:58 2018 -0700
@@ -86,7 +86,7 @@
   unwind_protect
     addpath (pwd);
     for n = 1:numel (arg.toolkits)
-      if (! isdir (fullfile (cwd, arg.toolkits{n})))
+      if (! isfolder (fullfile (cwd, arg.toolkits{n})))
         mkdir (arg.toolkits{n});
       endif
       cd (arg.toolkits{n});

--- a/scripts/testfun/rundemos.m	Mon Aug 13 11:41:17 2018 -0700
+++ b/scripts/testfun/rundemos.m	Mon Aug 13 12:17:58 2018 -0700
@@ -38,7 +38,7 @@
     do_class_dirs = true;
   elseif (nargin == 1)
     dirs = {canonicalize_file_name(directory)};
-    if (isempty (dirs{1}) || ! isdir (dirs{1}))
+    if (isempty (dirs{1}) || ! isfolder (dirs{1}))
       ## Search for directory name in path
       if (directory(end) == '/' || directory(end) == '\')
         directory(end) = [];
@@ -82,7 +82,7 @@
       endif
     elseif (f(1) == "@")
       f = fullfile (directory, f);
-      if (isdir (f))
+      if (isfolder (f))
         dirs(end+1) = f;
       endif
     endif

--- a/scripts/testfun/runtests.m	Mon Aug 13 11:41:17 2018 -0700
+++ b/scripts/testfun/runtests.m	Mon Aug 13 12:17:58 2018 -0700
@@ -38,7 +38,7 @@
     do_class_dirs = true;
   elseif (nargin == 1)
     dirs = {canonicalize_file_name(directory)};
-    if (isempty (dirs{1}) || ! isdir (dirs{1}))
+    if (isempty (dirs{1}) || ! isfolder (dirs{1}))
       ## Search for directory name in path
       if (directory(end) == '/' || directory(end) == '\')
         directory(end) = [];
@@ -83,7 +83,7 @@
       endif
     elseif (f(1) == "@")
       f = fullfile (directory, f);
-      if (isdir (f))
+      if (isfolder (f))
         dirs(end+1) = f;
       endif
     endif