Hi, try
library("dplyr") plot <- c(104, 104 ,104 ,104 ,104 ,105 ,105 ,105 ,105 ,105,106, 106,106, 106, 106,108, 108,108,108,108) lai <- c(82, 167, 248, 343, 377, 64, 139, 211, 296, 348, 94, 167,243,281,332,83, 382,320,146,129) leaf <- c(1,2, 3,4,5,1,2,3,4,5,1,2,3,4,5,1,2,3,4,5) df <- cbind(plot, lai, leaf) %>% data.frame() df %>% dplyr::group_by(plot) %>% dplyr::summarise(mean = mean(lai, na.rm = T)) Best, Frederick -----Original Message----- From: R-help [mailto:r-help-boun...@r-project.org] On Behalf Of Isaac Barnhart Sent: donderdag 14 februari 2019 15:32 To: r-help@r-project.org Subject: [R] Finding the Mean of a Specific Set of Columns I am having trouble finding the mean of a specific part of my dataset. Here is a sample of it: plot lai leaf 1 104 82 1 2 104 167 2 3 104 248 3 4 104 343 4 5 104 377 5 6 105 64 1 7 105 139 2 8 105 211 3 9 105 296 4 10 105 348 5 11 106 94 1 12 106 167 2 13 106 243 3 14 106 281 4 15 106 332 5 16 108 83 1 17 108 382 2 18 108 320 3 19 108 146 4 20 108 129 5 I have many different plot numbers, none of which follow any kind of specific numeric sequence (even though I have sorted them from smallest to largest). I need to take the average (mean) of the LAI for each plot, and was wondering if there was a way to specify the code to do this. For example: I need the average of all the LAI measurements for each leaf of plot 104, 105, etc. Any help would be appreciated. Thanks! Get Outlook for iOS<https://aka.ms/o0ukef> [[alternative HTML version deleted]] ______________________________________________ R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see 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. ______________________________________________ R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see 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.