Hello All, I am trying to do a simple thing of calculating the absolute difference between 2 previous values. Since my original data consists of 30 rows, this column where I am storing my absolute difference values only consists of 29 rows (called the ?differ?)! And I am having troubling cbind ing the 2 columns. Is there any way I can make the first row of ?differ? column as NA? So my data looks like following dput(data) tructure(list(week = c(1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30), value = c(9.45, 7.99, 9.29, 11.66, 12.16, 10.18, 8.04, 11.46, 9.2, 10.34, 9.03, 11.47, 10.51, 9.4, 10.08, 9.37, 10.62, 10.31, 10, 13, 10.9, 9.33, 12.29, 11.5, 10.6, 11.08, 10.38, 11.62, 11.31, 10.52)), .Names = c("week", "value"), row.names = c(NA, -30L), class = "data.frame") This is how I calculate my ?diff? column: differ <- abs(diff(data$value)) Which gives me the following results: [1] 1.46 1.30 2.37 0.50 1.98 2.14 3.42 2.26 1.14 1.31 2.44 0.96 [13] 1.11 0.68 0.71 1.25 0.31 0.31 3.00 2.10 1.57 2.96 0.79 0.90 [25] 0.48 0.70 1.24 0.31 0.79 As you can see this only contains 29 rows, so when I try to cbind it to my current data, I have an error. cbind(differ,data) Error in data.frame(..., check.names = FALSE) : arguments imply differing number of rows: 29, 30 What I ideally want is my new dataset to look as: Week Value Differ 1 9.45 NA 2 7.99 1.46 3 9.29 1.30 And so on?. *********************************************************************************************************************************************************************************************************************** MORE TH>N is a trading style of Royal & Sun Alliance Insurance plc (No. 93792). Registered in England and Wales at St. Mark’s Court, Chart Way, Horsham, West Sussex, RH12 1XL. Authorised by the Prudential Regulation Authority and regulated by the Financial Conduct Authority and the Prudential Regulation Authority. ************************************************************************************************************************************************************************************************************************ [[alternative HTML version deleted]]