Improve m2json; Support strings, datetime and convert -Inf to 'null', not '-null'

Author: robertoffmoura

plotly/plotly_aux/m2json.m

@@ -22,6 +22,7 @@
         elseif length(val) == 0
             valstr = '[]';
         end
+        valstr = strrep(valstr,'-Inf', 'null');
         valstr = strrep(valstr, 'Inf', 'null');
         valstr = strrep(valstr, 'NaN', 'null');
     elseif ischar(val)
@@ -39,6 +40,12 @@
         else
             valstr = 'false';
         end
+    elseif isdatetime(val)
+        valstr = m2json(convertDate(val));
+    elseif isstring(val)
+        fh = ifel(isscalar(val),@char,@cellstr);
+        valstr = m2json(fh(val));
     else
         valstr = ''; % wtf is it?
+        warning("Failed to m2json encode class of type: %s",class(val));
     end

plotly/plotlyfig_aux/helpers/convertDate.m

@@ -1,4 +1,27 @@
-function convertedDate = convertDate(date)
- date.Format = 'yyyy-MM-dd HH:mm:ss';
- convertedDate = char(date);
-end 
+function output = convertDate(date)
+    date = convertToDateTime(date);
+    if isDate(date)
+        format = "yyyy-mm-dd";
+    else
+        format = "yyyy-mm-dd HH:MM:ss";
+    end
+    output = string(date, format);
+end
+
+function dt = convertToDateTime(input)
+    if isdatetime(input)
+        return
+    elseif isnumeric(input)
+        % Assume input is a datenum
+        dt = datetime(input, 'ConvertFrom', 'datenum');
+    elseif ischar(input) || isstring(input)
+        % Assume input is a date string
+        dt = datetime(input);
+    else
+        error('Unsupported date type');
+    end
+end
+
+function tf = isDate(dt)
+    tf = all([hour(dt), minute(dt), second(dt)] == 0);
+end