This is not the natural order. In natural order hyphens ( representing the value zero ) should come between positive and negative values.
To achieve such custom orders, ExtJs allows you to define a sorting function. In your store, you would define someting like :
sorters: [{
sorterFn: function(value1, value2){
if (value1 === value2) {
return 0;
}
if (value1 == '-') return -1;
if (value2 == '-') return 1;
return parseFloat(value1) < parseFloat(value2) ? -1 : 1;
}
}]