Hi, I've two data.frame: ind_comp and dati_area
> ind_comp INDEX indice 1 1 0.3081856 2 2 0.1368007 3 3 0.1290952 4 4 0.2905484 5 5 0.2686706 6 6 0.1122784 7 7 0.4493264 8 8 0.1932665 9 9 0.1982783 10 11 0.3724666 > dati_area X_COORD Y_COORD DBH AREA ID ind_comp 1 0.0000000 0.0000000 70.0 1 1 0 2 4.4352788 14.5071431 70.0 1 2 0 3 10.6893894 10.3226234 68.0 1 3 0 4 5.8856279 0.4115632 75.5 1 4 0 5 5.7429111 -8.5142159 78.5 1 5 0 6 -6.4300000 11.1370867 60.0 1 6 0 7 0.6358819 -12.1333488 82.4 1 7 0 8 -7.9629934 -15.6282544 60.0 1 8 0 9 -7.9962383 -7.1998453 62.0 1 9 0 10 -17.3282497 5.6302896 67.0 1 10 0 11 -3.2569414 5.0152500 77.5 1 12 0 I need to populate the column "ind_comp" of the data.frame "dati_area", with the data "indice" of the data.frame "ind_comp". The data "INDEX" of the data.frame "ind_comp" must correspond to index of the rows "dati_area". X_COORD Y_COORD DBH AREA ID ind_comp 1 0.0000000 0.0000000 70.0 1 1 0.3081856 2 4.4352788 14.5071431 70.0 1 2 0.1368007 3 10.6893894 10.3226234 68.0 1 3 0.1290952 4 5.8856279 0.4115632 75.5 1 4 0.2905484 5 5.7429111 -8.5142159 78.5 1 5 0.2686706 6 -6.4300000 11.1370867 60.0 1 6 0.1122784 7 0.6358819 -12.1333488 82.4 1 7 0.4493264 8 -7.9629934 -15.6282544 60.0 1 8 0.1932665 9 -7.9962383 -7.1998453 62.0 1 9 0.1982783 10 -17.3282497 5.6302896 67.0 1 10 NA 11 -3.2569414 5.0152500 77.5 1 12 0.3724666 Thanks, Alfredo ______________________________________________ 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.