# [R] Finding the Mean of a Specific Set of Columns

Frederick Thielen th|e|en @end|ng |rom e@hpm@eur@n|
Thu Feb 14 17:36:43 CET 2019

```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-bounces using r-project.org] On Behalf Of Isaac Barnhart
Sent: donderdag 14 februari 2019 15:32
To: r-help using 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!

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