# [R] loops in R

Don McKenzie dmck at u.washington.edu
Wed Nov 5 19:02:11 CET 2014

```Have you read the tutorial that comes with the R distribution?  This is a very basic database calculation that you will
encounter (or some slight variation of it) over and over.  The solution is a few lines of code, and someone may write it
out for you, but if no one does

You have 20 populations, so you will have 20 iterations in your for loop. For each one, you will need a unique identifier that points to
the rows of “R” associated with that population. You’ll calculate a mean and variance 20 times, and will need a data object to store
those calculations.

Look in the tutorial for syntax for identifying subsets of your data frame.

> On Nov 5, 2014, at 5:41 AM, Noha Osman <nmo_138 at usc.edu> wrote:
>
> Hi Folks
>
> Iam  a new user of R and I have a question . Hopefully anyone help me in that issue
>
>
> I have that dataset as following
>
> Sample      Population  Species  Tissue         R         G        B
> 1 Bari1_062-1      Bari1     ret   seed  94.52303  80.70346 67.91760
> 2 Bari1_062-2      Bari1     ret   seed  98.27683  82.68690 68.55485
> 3 Bari1_062-3      Bari1     ret   seed 100.53170  86.56411 73.27528
> 4 Bari1_062-4      Bari1     ret   seed  96.65940  84.09197 72.05974
> 5 Bari1_062-5      Bari1     ret   seed 117.62474  98.49354 84.65656
> 6 Bari1_063-1      Bari1     ret   seed 144.39547 113.76170 99.95633
>
> and I have 20 populations as following
>
> [1] Bari1      Bari2      Bari3      Besev      Cermik     Cudi       Derici     Destek     Egil
> [10] Gunasan    Kalkan     Karabace   Kayatepe   Kesentas   Ortanca    Oyali      Cultivated Sarikaya
> [19] Savur      Sirnak
>
> I need to calculate mean and variance of each population using column [R] using  for-loop
>
>
> Thanks
>
> 	[[alternative HTML version deleted]]
>
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> and provide commented, minimal, self-contained, reproducible code.

Don McKenzie
Research Ecologist
Pacific Wildland Fire Sciences Lab
US Forest Service

Affiliate Faculty
School of Environmental and Forest Sciences
University of Washington
dmck at uw.edu

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