I have a "data frame" like this: Category Observed_value A 100 A 130 A 140 B 90 C 80 D 120 D 130
I need to create an index column that show the number of the observation for each category. I have three observations in the category A, one in category B, one in category C and two in category D. The new matrix should be like this: Category Observed_value Index A 100 1 A 130 2 A 140 3 B 90 1 C 80 1 D 120 1 D 130 2 Please, could anyone help me with this problem? Thank you. -- Marcos Martins Santos mmsantos...@gmail.com -- Skype: marcosmartinssantos [[alternative HTML version deleted]] ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.