While you should definitely read the tutorial that Don is referring to, I'd recommend you take a different approach and use more R idiomatic code here.
In base R, this could be addressed with few approaches. Look for help on the following functions: * tapply * by * aggregate I'd rather recommend you also learn about some of the packages that are better suited to deal with computing over data.frames, particularly: * dplyr * data.table You can certainly achieve what you want with for loops, but you'll likely find that going this route will be more rewarding in the long run. HTH, -steve On Wed, Nov 5, 2014 at 10:02 AM, Don McKenzie <[email protected]> wrote: > 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 <[email protected]> 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]] >> >> ______________________________________________ >> [email protected] mailing list >> 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. > > Don McKenzie > Research Ecologist > Pacific Wildland Fire Sciences Lab > US Forest Service > > Affiliate Faculty > School of Environmental and Forest Sciences > University of Washington > [email protected] > > ______________________________________________ > [email protected] mailing list > 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. -- Steve Lianoglou Computational Biologist Genentech ______________________________________________ [email protected] mailing list 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.
