I have a table of data that I want to add an extra line to, indicating if two variables stay the same or if one of them changes.   For example if I had a table like this:    A 1 A 1 A 2 A 3 B 1 B 1 B 4 C 1 C 2 C 2   I would want to add a new column starting at 1 and going up by 1 every time either column 1 or column 2 changes. In the example this would create the following result:   A 1 1 A 1 1 A 2 2 A 3 3 B 1 4 B 1 4 B 4 5 C 1 6 C 2 7 C 2 7   The real dataset is much larger than this, about 400.000 entries, but the principle remains the same. I need an automated and scalable solution. I figured I could turn the columns into arrays, use a for loop to create column 3 and add it to the dataset, but was not able to figure this out.    Any help is appreciated, cheers!   ... View more