Thank you Sarah for this code, it's exactly what I wanted to reach. Le 05/06/2013 16:49, Sarah Goslee a écrit :
What about using instead size = min(5, length(Gpool$SampleNb[Gpool$LngtClas == LngtClas[[4]]& Gpool$SpCode == SpCode[[2]]]) that would make sure your sample is either the size of the data or 5. Sarah On Wed, Jun 5, 2013 at 10:27 AM, Xochitl CORMON <xochitl.cor...@ifremer.fr> wrote:Hi all, I'm trying to randomly select sample numbers for length class groups (5 per length class). For this I'm using a loop FOR and the function sample () and specified a size for the sampling of 5. Unfortunately, one of the length class group does not contain 5 individuals. For me is not a big deal as I have others groups to complete. However it bothers me that the sampling function does not select any individuals in this group generating the error below : Error in sample(Gpool2$SampleNb[Gpool2$LngtClas == LngtClas[[i]]& Gpool2$SpCode == : can not take a sample larger than the population when 'replace = FALSE'. I understand why this error message appears but I was wondering if there is a way to select all the items present in the group even if it's not 5 (something like size =< 5). LngtClas<- list( "40_49", "50_59", "60_69", "70_") SpCode<- list ("POLLVIR ", "MERLMER") a<- as.character(sample(Gpool$SampleNb[Gpool$LngtClas == LngtClas[[4]]& Gpool$SpCode == SpCode[[2]]], size = 5, replace = FALSE)) You can find enclosed my dataset, Thank you for the help, Xochitl C.
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