Hi again to everybody, I incountered the following error when I try to make a sample inside a dataset. My code is:
> data_ostrya <- sample(ostrya,200, replace=F) Error in `[.data.frame`(x, .Internal(sample(length(x), size, replace, : cannot take a sample larger than the population when 'replace = FALSE' Why it does not work? The whole dataset is composed of 536 rows and I just want to sample randomly 200 of them... Thank you in advance, Gian On 13 September 2012 14:01, Duncan Murdoch <murdoch.dun...@gmail.com> wrote: > On 12-09-13 7:43 AM, Gian Maria Niccolò Benucci wrote: > >> Thank you Duncan, >> >> I got the result of sampling, but it gave me only the row numbers. Is it >> possible to have the entire row with variables and other information? >> Because I need to re-sample inside my matrix the whole rows in reason to >> have 20 samples (i.e., rows) each year. >> Thank you for your invaluable help! >> > > Use those row numbers to index the dataframe or matrix, e.g. > > a[rows,] > > Duncan Murdoch > > >> Gian >> >> >> On 13 September 2012 13:32, Duncan Murdoch <murdoch.dun...@gmail.com> >> wrote: >> >> On 12-09-13 7:18 AM, Gian Maria NiccolÅ Benucci wrote: >>> >>> Thank you very much for your help, >>>> >>>> I was wondering if is possible to sample randomly specifying to select >>>> in >>>> a >>>> particular group of data inside the matrix, for example only within the >>>> whole samples collected in 2011 I would randomly choose 20 random >>>> samples... >>>> >>>> >>> You need two steps: find the rows that meet your condition, then sample >>> from those. For example, >>> >>> rows <- which( a$year == 2011 ) >>> sample(rows, 20) >>> >>> There is one thing to watch out for: if you have a condition that only >>> matches one row, you will get unexpected results here, because the sample >>> will be taken from 1:rows. See the examples in ?sample for the >>> workaround >>> that uses sample.int. >>> >>> Duncan Murdoch >>> >>> >>> Thanks a again, >>>> >>>> >>>> Gian >>>> >>>> On 13 September 2012 12:26, anna freni sterrantino <annafr...@yahoo.it >>>> >>>>> wrote: >>>>> >>>> >>>> Hello Gian, >>>> >>>>> sure sample function >>>>> will do it for your sampling. >>>>> >>>>> a=as.data.frame(matrix(1:20,4)****) >>>>> >>>>> sample(rownames(a),2) >>>>> >>>>> see ?sample for more details. >>>>> Hope it helps >>>>> >>>>> Cheers >>>>> >>>>> Anna >>>>> >>>>> >>>>> Anna Freni Sterrantino >>>>> Department of Statistics >>>>> University of Bologna, Italy >>>>> via Belle Arti 41, 40124 BO. >>>>> ------------------------------ >>>>> *Da:* Gian Maria NiccolÅ Benucci <gian.benu...@gmail.com> >>>>> *A:* r-help@r-project.org >>>>> *Inviato:* GiovedÄ 13 Settembre 2012 10:42 >>>>> *Oggetto:* [R] random sampling inside a dataset >>>>> >>>>> >>>>> Hi all, >>>>> >>>>> I am wondering if do exist a function in R that allow me to sample or >>>>> choose randomly the rows (i.e., samples) inside a given matrix. >>>>> Thank you very much in advance. >>>>> Cheers, >>>>> >>>>> -- >>>>> Gian >>>>> >>>>> [[alternative HTML version deleted]] >>>>> >>>>> ______________________________****________________ >>>>> R-help@r-project.org mailing list >>>>> https://stat.ethz.ch/mailman/****listinfo/r-help<https://stat.ethz.ch/mailman/**listinfo/r-help> >>>>> <https://stat.**ethz.ch/mailman/listinfo/r-**help<https://stat.ethz.ch/mailman/listinfo/r-help> >>>>> > >>>>> >>>>> PLEASE do read the posting guide >>>>> http://www.R-project.org/****posting-guide.html<http://www.R-project.org/**posting-guide.html> >>>>> <http://www.**R-project.org/posting-guide.**html<http://www.R-project.org/posting-guide.html> >>>>> > >>>>> <http://www.**r-project.org/**posting-guide.**html<http://r-project.org/posting-guide.**html> >>>>> <http://**www.r-project.org/posting-**guide.html<http://www.r-project.org/posting-guide.html> >>>>> > >>>>> >>>>> >>>>>> >>>>> and provide commented, minimal, self-contained, reproducible code. >>>>> >>>>> >>>>> >>>>> >>>>> >>>> >>>> >>>> This body part will be downloaded on demand. >>>> >>>> >>>> >>> >> >> > [[alternative HTML version deleted]]
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