Add writetable function

* inst/dbtable.m: add writetable

* inst/private/write_dbtable_csv.m: new file

Author: lostbard

inst/dbtable.m

@@ -463,6 +463,20 @@ function summary (this)
       endfor
     endfunction
 
+    function writetable (this, filename)
+      [~, ~, ext] = fileparts(filename);
+      if isempty(ext)
+        ext = ".csv"
+      endif
+
+      switch tolower(ext)
+        case { ".txt" ".csv" ".dat" }
+          write_dbtable_csv(this, filename);
+        otherwise
+          error ("unknown or unsupported format for '%s'", ext); 
+      endswitch
+    endfunction
+
     # head tail - create sub tables
     function tdata = head(this, rows)
       nrows = size(this, 1);

inst/private/write_dbtable_csv.m

@@ -0,0 +1,68 @@
+## Copyright (C) 2022 John Donoghue <john.donoghue@ieee.org>
+##
+## This program 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.
+##
+## This program 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 this program.  If not, see
+## <https://www.gnu.org/licenses/>.
+
+## -*- texinfo -*- 
+## @deftypefn {} {@var{t} =} write_dbtable_csv (@var{filename})
+## Private function
+## @end deftypefn
+
+function write_dbtable_csv (t, filename)
+  fd = fopen(filename, "wt");
+  if fd == -1
+    error ("Error opening file '%s'", filename);
+  endif
+  unwind_protect
+    cols = subsref (t, substruct(".", "Properties")).VariableNames;
+    l = strjoin(cols, ",");
+    fprintf(fd, "%s\n", l);
+
+    for idx = 1:length(t)
+      row = subsref (t, substruct("{}", {idx,':'}));
+      values = "";
+      for col=1:numel(cols)
+        if col > 1
+          values = [values ","];
+        endif
+        if iscell(row)
+          v = row{col}{:};
+        else
+          v = row(col,:);
+        endif
+        if islogical(v)
+          if v
+            v = 1;
+          else
+            v = 0;
+          endif
+        endif
+        if isnumeric(v)
+           v = num2str(v);
+        elseif isempty(v)
+           v = "";
+        endif
+        # quote it if spaces
+        if !isempty(strchr(v, " "))
+          v = ['"' v '"'];
+        endif
+        values = [values v];
+      endfor
+      fprintf(fd, "%s\n", char(values));
+    endfor
+
+  unwind_protect_cleanup
+    fclose(fd);
+  end_unwind_protect
+endfunction