The simplest way to hide columns is setting column count property to the smaller number than actual number of fields in the dataset
var myCells = [
["Some text", "123", "456.00"]
];
...
obj.setColumnCount(2);
In addition it is possible to specify exactly which columns should be rendered by providing an array of column indices.
obj.setColumnIndices([1,2,3]); // column 0 is hidden
obj.setColumnCount(3);
Class reference - column count, column indices