Hi David, Thank you for the insight: I could have sworn I added a picture of the data, but providing the actual data is worlds easier to deal with, I'm sure. I've never used dput(), so I entered it using the dataframe in question as the object, and I've pasted the results below.
Essentially, I would like to run the two-sample independent test, comparing Group 5 (CD8.14 through CD8.17) to Group 6 (CD8.18 through CD8.21). So, for A, test Group 5 agains Group 6, for B, test Group 5 against Group 6, and so on. I'm not going to muddy the waters by telling you what I've tried; suffice it to say that I'm looking for insights into how to structure R commands to compare groups of data of this format. Many thanks in advance, David structure(list(Gene = structure(c(1L, 12L, 19L, 20L, 21L, 22L, 23L, 24L, 25L, 2L, 3L, 4L, 5L, 6L, 7L, 8L, 9L, 10L, 11L, 13L, 14L, 15L, 16L, 17L, 18L), .Label = c("CD8.1", "CD8.10", "CD8.11", "CD8.12", "CD8.13", "CD8.14", "CD8.15", "CD8.16", "CD8.17", "CD8.18", "CD8.19", "CD8.2", "CD8.20", "CD8.21", "CD8.22", "CD8.23", "CD8.24", "CD8.25", "CD8.3", "CD8.4", "CD8.5", "CD8.6", "CD8.7", "CD8.8", "CD8.9"), class = "factor"), Group = structure(c(8L, 8L, 8L, 9L, 9L, 9L, 10L, 10L, 10L, 11L, 11L, 11L, 11L, 12L, 12L, 12L, 12L, 13L, 13L, 13L, 13L, 14L, 14L, 14L, 14L), .Label = c("Fabbf Ova CD40", "Fabbf Ova MHC2", "Fabbf Ova WT", "Fabbf WT", "Naïve CD40", "Naïve MHC II", "Naïve WT", "1", "2", "3", "4", "5", "6", "7"), class = "factor"), A = c(19.4701946749544, 0.679440926463348, 0.69035683372563, 0.347105466158261, 0.435480792190284, 0.338699910286907, 0.651378057031152, 0.707065053752258, 0.685244609506316, 0.816673858871597, 0.597009097584509, 0.592331304482431, 0.709359033358704, 0.628406759227531, 0.78158729467231, 1.0422377526669, 0.61560003251142, 0.463755016733183, 0.419700860701392, 0.380946898502731, 0.41156961153081, 0.471790683365624, 0.552773224145722, 0.466787799928649, 0.767624372542755), B = c(1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1), C = c(0.914649979331863, 1.443086801592, 0.928280641141244, 0.467498974059775, 0.668742025741347, 0.568417298005388, 0.778907650835673, 0.778765181169635, 1.01103488277517, 0.674133483128923, 0.830400022230133, 0.652687178870627, 0.746893950266518, 0.765498308522646, 1.01273201749333, 1.00309616129672, 0.63015975419947, 0.615905247119739, 0.615687625199691, 0.503136087800137, 0.566164026974035, 0.631519467967541, 0.822126705285366, 0.543873075815645, 1.00596108625425), D = c(13.3272657341526, 3.08914950309865, 1.71836820240434, 0.723301573710509, 1.21014411624732, 1.92899377364865, 1.80280408189187, 2.25057819266424, 2.23876060313374, 1.30849425313072, 1.58782967140617, 1.19199809794126, 1.64151140806787, 0.241017500596534, 0.364896032519483, 0.322953808735804, 0.2052110581509, 0.927601295331376, 0.808910781520832, 0.538033121081646, 0.655348783504307, 0.564449549672088, 0.521729926793001, 0.414305517285192, 0.507084483980948), E = c(56.2830291897158, 9.76091939190267, 4.80922410182105, 17.0056576949022, 20.851046177766, 17.9057247086369, 5.93332779160845, 4.73058157592946, 5.59155211460608, 9.67484467290805, 5.92374864612388, 7.12393623733123, 5.33576126730867, 10.3943422629275, 10.8732527705049, 12.4861085370674, 12.0918705721064, 13.3210661695018, 10.9410344557684, 15.1298307761675, 13.0708078246191, 9.4445293976312, 6.94340249514349, 5.07888688780375, 8.33846787814466 ), F = c(15.0459568981729, 21.6362955612539, 9.66673955488981, 27.2276698483913, 18.1090094072926, 20.0952712980862, 24.9249499974856, 23.5540183530194, 29.6638363657906, 28.9779309040733, 42.0402820641407, 33.8068160394092, 51.7299064374737, 37.8306751403421, 43.1955470199259, 45.5125262939585, 40.3109474523637, 23.6341894633273, 23.9721353180788, 20.4920649252818, 24.8898447627354, 34.2686409607416, 31.3815198841165, 31.4947528368753, 43.2686436885025), G = c(15.9703031418086, 5.30495997585743, 3.07594974529074, 8.28703732907722, 10.9437825143868, 6.91196232523896, 2.97808148581742, 2.6386825521864, 2.2415006913088, 5.00747306438661, 2.65238188782831, 3.18277515130905, 3.14638620532385, 2.5149505923191, 2.48862112414046, 2.97170069886913, 1.91643165326171, 7.50682774199005, 5.39102206185423, 5.2498453524987, 7.17519969844757, 2.66448841457179, 2.78444235996995, 1.62286520735228, 2.48760726398266 ), H = c(-1, -1, -1, 0.0036561124481055, 0.010723007432761, 0.0196616746380801, 0.0371046164124276, -1, 3.27378673314144e-05, -1, -1, -1, -1, 0.00816215783906802, 21.5424904701651, 9.57900616157724, 0.00735942043489242, 1.50346040901698, 0.0909450037365435, 1.49237001404701e-05, 0.000775741472561218, -1, 17.9023582944659, 0.0176891314806093, 33.4326253626981)), .Names = c("Gene", "Group", "A", "B", "C", "D", "E", "F", "G", "H"), row.names = c(NA, 25L), class = "data.frame") -- View this message in context: http://r.789695.n4.nabble.com/Mann-Whitney-by-group-tp4635618p4635667.html Sent from the R help mailing list archive at Nabble.com. ______________________________________________ R-help@r-project.org 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.