QGis Making Column Value of Attribute table unique

For a shapefile, I have a field named id with the following contents in it:

1
1

2
2

I want to make these values unique such as:

1
2
3
4

Is there any way to achieve this in Quantum GIS (using any plugin or other means) ?

Answer

You can use the Field Calculator in the Attribute table to assign the features unique values by checking "Update existing field", selecting the appropriate field, and entering $rownum in the Expression box. This will assign each feature its row number as its ID.