Only a quick suggestion (I don't understand what you tried, or trying to tell - lost in translation?):
Read in your XML to a internal representation of your data.
e.g. something like this
class Control
{
public DateTime Date { get; set; }
public double[] Values { get; set; }
public double Avarage { get; set; }
public double Expanse { get; set; }
}
...add the instances to a list
List<control> listControls;</control>
...bind them to your datagrid
datagrid.ItemsSource = listControls;