Message-ID: <BN6PR05MB33802603B26D487B4A34E7DFAE670@BN6PR05MB3380.namprd05.prod.outlook.com>
Date: 2019-02-14T19:34:57Z
From: Isaac Barnhart
Subject: Finding the Mean of a Specific Set of Columns
In-Reply-To: <3344F7AE-92EB-4E3E-A2FA-30D231861891@me.com>
Thanks for the help!
Isaac
________________________________
From: Marc Schwartz <marc_schwartz at me.com>
Sent: Thursday, February 14, 2019 11:05:23 AM
To: Isaac Barnhart
Cc: R-help
Subject: Re: [R] Finding the Mean of a Specific Set of Columns
On Feb 14, 2019, at 9:31 AM, Isaac Barnhart <ihb at ksu.edu> wrote:
>
> 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!
Hi,
This is easy using base R functions. See ?aggregate, ?by and ?tapply for a starting place.
For example:
> aggregate(lai ~ plot, data = DF, FUN = mean)
plot lai
1 104 243.4
2 105 211.6
3 106 223.4
4 108 212.0
Regards,
Marc Schwartz
[[alternative HTML version deleted]]