Hello Bui,

Thank you for posting in our forum.

You can transpose columns and rows as follows.

1. Transpose columns and rows in existing igOlapFlatDataSource option.
2. Create new igOlapFlatDataSource with the option.
3. Update igPivotView dataSource to new igOlapFlatDataSource.

// When initializing
var option = {
・・・
rows: "[Date].[Dates]",
columns: "[Seller].[Seller]",
・・・
};
var ofds = new $.ig.OlapFlatDataSource(option);
$("#pivotView").igPivotView({
dataSource: ofds,
・・・
});

// When transposing
var rows = option.rows;
var columns = option.columns;
option.rows = columns;
option.columns = rows;
var ofds = new $.ig.OlapFlatDataSource(option);
$('#pivotView').igPivotView('option', 'dataSource', ofds);

About keeping expanded, there is no option or functionality to persist it.
So you should expand columns and rows manually calling expandTupleMember method.

https://jp.igniteui.com/help/api/2016.2/ui.igPivotGrid#methods:expandTupleMember

I hope this will help.
If you need further assistance, please let me know.

Best Regards,
Tatsushi Kiryu
Developer support Engineer
Infragistics