Here is my code:

var Kalliertable = $('#FKall').DataTable({
     
      ajax: {
        url: 'php/table.KallierFromCust.php',
        type: 'post',
        data: function(d) {
          var selected = custtable.row({
            selected: true
          });
          if (selected.any()) {
            d.Cust = selected.data().Id;
          }
        }
      },
      order: [
        [6, 'asc']
      ],
      rowGroup: {
        startRender: null,
        endRender: function(rows, group) {        

          var ageAvg = rows
                .data()
                .pluck(4)
                .reduce( function (a, b) {
                    return a + b*1;
                }, 0) / rows.count();

            var salaryAvg = rows
                .data()
                .pluck(5)
                .reduce( function (a, b) {
                    return a + b.replace(/[^\d]/g, '')*1;
                }, 0) / rows.count();
            salaryAvg = $.fn.dataTable.render.number(',', '.', 0, '$').display( salaryAvg );

            return $('<tr/>')
                .append( '<td colspan="3">Averages for '+group+'</td>' )
                .append( '<td>'+ageAvg.toFixed(0)+'</td>' )
                .append( '<td/>' )
                .append( '<td>'+salaryAvg+'</td>' );
                  },
        dataSrc: 'Kallier.kindkall'
      },
      columns: [{
          "data": "Kallier.id"
        },
        {
          "data": "Kallier.codefiel"
        },
        {
          "data": "Field.codeklhr",
          render: function(toFormat) {
            var tKliros;
            tKliros = toFormat.toString();
            tKliros = tKliros.substring(0, 1) + '-' + tKliros.substring(1, 4) + '/' + tKliros.substring(4, 10);
            return tKliros
          }
        },
        {
          data: null,
          render: function(data, type, row) {
            // Combine the first and last names into a single table field
            return data.Cust.custepon + ' ' + data.Cust.custname;
          }
        },
        {
          "data": "Kallier.ektashka"
        },
        {
          "data": "Kallier.kallxrev"
        },
        {
          "data": "Kallier.kindkall"
        },
        {
          "data": "Kallier.codecust",
          "visible": false
        }

      ],
      select: true,
      lengthChange: true,
      buttons: [

      ],
      language: {
        thousands: ".",
        decimal: ",",
        processing: "Traitement en cours...",
        search: "Αναζήτηση&nbsp;:",
        lengthMenu: "Εμφάνιση _MENU_ εγγραφών",
        info: "Εμφάνιση _START_ Από _END_ από σύνολο _TOTAL_ εγγραφών",
        infoEmpty: "Εμφάνιση  0 Από 0 από σύνολο 0 εγγραφών",
        infoFiltered: "(Ευρεθείσες εγγραφές από _MAX_ συνολικά)",
        infoPostFix: "",
        loadingRecords: "Φόρτωση Δεδομένων...",
        zeroRecords: "Δεν υπάρχουν εγγραφές!",
        emptyTable: "Δεν υπάρχουν εγγραφές σε αυτόν τον πίνακα!",
        paginate: {
          first: "Πρώτη",
          previous: "Προηγούμενη",
          next: "Επόμενη",
          last: "Τελευταία"
        },
        aria: {
          sortAscending: ": activer pour trier la colonne par ordre croissant",
          sortDescending: ": activer pour trier la colonne par ordre décroissant"
        }
      },

      "footerCallback": function(row, data, start, end, display) {
        var api = this.api(),
          data;

        // Remove the formatting to get integer data for summation
        var intVal = function(i) {
          return typeof i === 'string' ?
            i.replace(/[\$,]/g, '') * 1 :
            typeof i === 'number' ?
            i : 0;
        };

        // Total over all pages
        total = api
          .column(4)
          .data()
          .reduce(function(a, b) {
            return intVal(a) + intVal(b);
          }, 0);

        // Total over this page
        pageTotal = api
          .column(4, {
            page: 'current'
          })
          .data()
          .reduce(function(a, b) {
            return intVal(a) + intVal(b);
          }, 0);

        // Update footer
        var num = $.fn.dataTable.render.number(',', '.', 4, '').display(pageTotal);
        var numT = $.fn.dataTable.render.number(',', '.', 4, '').display(total);
        $(api.column(2).footer()).html(
          ' ' + num + ' ( ' + numT + ' Σύνολο)'
        );
      }
    });

i get this error:
Uncaught TypeError: Cannot read property 'replace' of undefined in line ... where i have this part of code:

return a + b.replace(/[^\d]/g, '')*1;

My data:

{"data":[{"DT_RowId":"row_1542","Kallier":{"id":"1542","codefiel":"1551","owner":"2335","ektashka":"6.250","kallxrev":"281.00","kindkall":"\u0394\u0395\u039d\u0394\u03a1\u0391 \u0394\u0399\u0391\u03a6\u039f\u03a1\u0391","codecust":"9"},"Field":{"codeklhr":"00011551"},"Cust":{"custepon":"\u0392\u039b\u0391\u03a7\u039f\u03a3 \u039d\u0395\u039d\u039f\u0393\u039b\u039f\u03a5","custname":"\u03a3\u03a4\u0395\u03a1\u0393\u0399\u039f\u03a3 \u0391\u03a1\u0399\u03a3\u03a4\u0395"}},{"DT_RowId":"row_1556","Kallier":{"id":"1556","codefiel":"1565","owner":"1142","ektashka":"4.003","kallxrev":"180.00","kindkall":"\u0394\u0395\u039d\u0394\u03a1\u0391 \u039f\u03a0\u03a9\u03a1\u039f\u03a6\u039f\u03a1\u0391","codecust":"9"},"Field":{"codeklhr":"00011565"},"Cust":{"custepon":"\u0398\u0395\u039f\u0394\u03a9\u03a1\u0399\u0394\u0397\u03a3","custname":"\u0391\u039d\u03a4\u03a9\u039d\u0399\u039f\u03a3"}},{"DT_RowId":"row_2352","Kallier":{"id":"2352","codefiel":"2362","owner":"1730","ektashka":"5.250","kallxrev":"236.00","kindkall":"\u0394\u0395\u039d\u0394\u03a1\u0391 \u039f\u03a0\u03a9\u03a1\u039f\u03a6\u039f\u03a1\u0391","codecust":"9"},"Field":{"codeklhr":"000213"},"Cust":{"custepon":"\u0392\u039b\u0391\u03a7\u039f\u03a5","custname":"\u03a3\u03a4\u0391\u039c\u0391\u03a4\u0399\u0391"}},{"DT_RowId":"row_2913","Kallier":{"id":"2913","codefiel":"1551","owner":"2335","ektashka":"0.636","kallxrev":"28.00","kindkall":"\u0394\u0395\u039d\u0394\u03a1\u0391 \u0394\u0399\u0391\u03a6\u039f\u03a1\u0391","codecust":"9"},"Field":{"codeklhr":"00011551"},"Cust":{"custepon":"\u0392\u039b\u0391\u03a7\u039f\u03a3 \u039d\u0395\u039d\u039f\u0393\u039b\u039f\u03a5","custname":"\u03a3\u03a4\u0395\u03a1\u0393\u0399\u039f\u03a3 \u0391\u03a1\u0399\u03a3\u03a4\u0395"}},{"DT_RowId":"row_3087","Kallier":{"id":"3087","codefiel":"2935","owner":"2231","ektashka":"2.300","kallxrev":"75.00","kindkall":"\u0394\u0395\u039d\u0394\u03a1\u0391 \u039c\u0399\u039a\u03a1\u0391","codecust":"9"},"Field":{"codeklhr":"10018"},"Cust":{"custepon":"\u03a4\u03a1\u0399\u0392\u0399\u0391\u0397\u03a3","custname":"\u0394\u0397\u039c\u0397\u03a4\u03a1\u0399\u039f\u03a3"}},{"DT_RowId":"row_4346","Kallier":{"id":"4346","codefiel":"1551","owner":"2335","ektashka":"1.500","kallxrev":"10.00","kindkall":"\u03a0\u0391\u0393\u0399\u039f","codecust":"9"},"Field":{"codeklhr":"00011551"},"Cust":{"custepon":"\u0392\u039b\u0391\u03a7\u039f\u03a3 \u039d\u0395\u039d\u039f\u0393\u039b\u039f\u03a5","custname":"\u03a3\u03a4\u0395\u03a1\u0393\u0399\u039f\u03a3 \u0391\u03a1\u0399\u03a3\u03a4\u0395"}}],"options": ...

etc.
As i can see the function doesn't work in data as '2.300' or '75.00'.
How can i fix this?
Thanks
I have to say that the results in footer are Ok