Updated to the numeric comma type detection - period allowed for decimal place and negative checking simplified.

Note added that the formatted numbers plug-in is preferable now.

sorting/numeric-comma.js

@@ -3,6 +3,10 @@
  * decimal place. This sorting plug-in shows how that can be taken account of in
  * sorting by adding the type 'numeric-comma' to DataTables. A type detection 
  * plug-in for this sorting method is provided below.
+ * 
+ * Please note that the 'Formatted numbers' type detection and sorting plug-ins
+ * offer greater flexibility that this plug-in and should be used in preference
+ * to this method.
  *  @name Commas for decimal place
  *  @anchor numeric_comma
  *  @author <a href="http://sprymedia.co.uk">Allan Jardine</a>

type-detection/numeric-comma.js

@@ -1,6 +1,10 @@
 /**
  * Automatically detect numbers which use a comma in the place of a decimal 
  * point to allow them to be sorted numerically.
+ * 
+ * Please note that the 'Formatted numbers' type detection and sorting plug-ins
+ * offer greater flexibility that this plug-in and should be used in preference
+ * to this method.
  *  @name Commas for decimal place
  *  @anchor numeric_comma
  *  @author <a href="http://sprymedia.co.uk">Allan Jardine</a>
@@ -9,28 +13,24 @@
 jQuery.fn.dataTableExt.aTypes.unshift(
 	function ( sData )
 	{
-		var sValidChars = "0123456789-,";
+		var sValidChars = "0123456789,.";
 		var Char;
 		var bDecimal = false;
+		var iStart=0;
+
+		/* Negative sign is valid - shift the number check start point */
+		if ( sData.charAt(0) === '-' ) {
+			iStart = 1;
+		}
 		 
 		/* Check the numeric part */
-		for ( i=0 ; i<sData.length ; i++ )
+		for ( i=iStart ; i<sData.length ; i++ )
 		{
 			Char = sData.charAt(i);
 			if (sValidChars.indexOf(Char) == -1)
 			{
 				return null;
 			}
-			 
-			/* Only allowed one decimal place... */
-			if ( Char == "," )
-			{
-				if ( bDecimal )
-				{
-					return null;
-				}
-				bDecimal = true;
-			}
 		}
 		 
 		return 'numeric-comma';