Calculating a Total for a Grid - rally

Question

I have a grid of the which has actual time as one of its columns. How can I add the rows up to get the total actual time similar to the way it is done on the track team status page.
Edit:
I am currently trying to find the sum using this var sum = grid.getStore().sum('Actuals');, however when I run it, I get this error on the console:
Uncaught ReferenceError: grid is not defined
I have also tried using this piece of code that I found online:
var tasks = [];
var users = [];
that = this
if (data.length ===0) {
this._createGrid(); //to refresh grid when no items in iteration
}
Ext.Array.each(this.tasks, function(task) {
var owner = task.get('Owner');
var total;
Ext.Array.each(data, function(actual){
//some tasks have no owner. If this condition is not checked Uncaught TypeError: Cannot read property '_refObjectName' of null
if (owner && actual.get('User')._refObjectName === owner._refObjectName) {
total = actual.get('Actuals');
}
});
var t = {
FormattedID: task.get('FormattedID'),
_ref: task.get("_ref"),
Name: task.get('Name'),
Estimate: task.get('Actuals'),
Owner: (owner && owner._refObjectName) || 'None',
TaskEstimates: total
};
tasks.push(t);
});
},
but when I try to print total or taskestimate or attempt to find a specific part of tasks (tasks[i][j]) I either get no data or an error

Answer 1

See a not-treegrid code in this post for an example of how to create a row in a grid that sums up values in a specific column (e.g. Estimate)
columnCfgs: [
{
xtype: 'templatecolumn',text: 'ID',dataIndex: 'FormattedID',width: 100,
tpl: Ext.create('Rally.ui.renderer.template.FormattedIDTemplate'),
summaryRenderer: function() {
return "Estimate Total";
}
},
{
text: 'Estimate',dataIndex: 'Estimate',
summaryType: 'sum',
}