Thanks - it made me realize that I had reversed the column and row selection
rowMeans(x[seq(1:dim(x)[1],by=4),-1]) Jim On Thu, Nov 10, 2016 at 8:30 AM, Uwe Ligges <lig...@statistik.tu-dortmund.de> wrote: > > > On 09.11.2016 22:06, Jim Lemon wrote: >> >> Hi Milu, >> Perhaps this will help: >> >> apply(as.matrix(x[-1,seq(1:dim(x)[1],by=4)]),1,mean) > > > More efficient than apply(..., 1, mean): rowMeans() > > Best, > Uwe Ligges > > > > >> >> Jim >> >> >> On Thu, Nov 10, 2016 at 4:00 AM, Miluji Sb <miluj...@gmail.com> wrote: >>> >>> Thanks a lot for your quick reply. I made a mistake in the question, I >>> meant to ask every 4 (or 12) rows not columns. Apologies. Thanks again! >>> >>> Sincerely, >>> >>> Milu >>> >>> On Wed, Nov 9, 2016 at 5:45 PM, Dalthorp, Daniel <ddalth...@usgs.gov> >>> wrote: >>> >>>> Hi Milu, >>>> The following should work for an array x (provided dim(x)[2] is >>>> divisible >>>> by 4): >>>> >>>> colMeans(x[,0:(dim(x)[2]/4-1)*4+1]) >>>> >>>> -Dan >>>> >>>> On Wed, Nov 9, 2016 at 8:29 AM, Miluji Sb <miluj...@gmail.com> wrote: >>>> >>>>> Dear all, >>>>> >>>>> I have a dataset with hundreds of columns, I am only providing only 12 >>>>> columns. Is it possible to take the mean of every four (or 12) columns >>>>> (value601, value602, value603, value604 etc.in this case) and repeat >>>>> for >>>>> the hundreds of columns? Thank you. >>>>> >>>>> Sincerely, >>>>> >>>>> Milu >>>>> >>>>> structure(list(value601 = c(10.1738710403442, 3.54112911224365, >>>>> 12.9192342758179, 3.17447590827942, 11.7332258224487, 7.68282270431519, >>>>> -7.11564493179321, 0.987620949745178, 13.0476207733154, >>>>> 6.36939525604248 >>>>> ), value602 = c(13.0642414093018, 5.53129482269287, 16.0519638061523, >>>>> 2.88946437835693, 14.9204912185669, 9.42428588867188, >>>>> -6.80674123764038, >>>>> -0.614241063594818, 16.7947769165039, 7.9541072845459), value603 = >>>>> c(22.0399188995361, >>>>> 14.398024559021, 24.9523792266846, 12.0878629684448, 23.6459674835205, >>>>> 18.3277816772461, -2.54092741012573, 10.5550804138184, >>>>> 25.1016540527344, >>>>> 16.2166938781738), value604 = c(27.7165412902832, 20.3255825042725, >>>>> 30.8430004119873, 16.6856250762939, 29.2485408782959, 24.3775005340576, >>>>> 6.47758340835571, 15.5897912979126, 30.7387924194336, 22.3637084960938 >>>>> ), value605 = c(31.6644763946533, 23.4093952178955, 35.1488723754883, >>>>> 19.7132263183594, 33.3924179077148, 29.5846366882324, 10.2083873748779, >>>>> 19.3551616668701, 35.3076629638672, 27.4299201965332), value606 = >>>>> c(33.9698333740234, >>>>> 26.8574161529541, 36.8900833129883, 22.8604583740234, 34.8642921447754, >>>>> 33.8158760070801, 14.7055835723877, 22.1144580841064, 37.0545425415039, >>>>> 32.1087913513184), value607 = c(36.0279846191406, 26.9297180175781, >>>>> 38.2701225280762, 23.2643146514893, 36.7398796081543, 34.1216125488281, >>>>> 17.1387901306152, 24.0419750213623, 37.8542327880859, 32.7677421569824 >>>>> ), value608 = c(34.0242347717285, 25.7720966339111, 36.4897193908691, >>>>> 22.0332260131836, 34.8011703491211, 32.6856842041016, 16.6232261657715, >>>>> 21.5571365356445, 36.1491546630859, 31.1716938018799), value609 = >>>>> c(27.5402088165283, >>>>> 21.7590408325195, 30.5214176177979, 18.4252090454102, 29.1156253814697, >>>>> 26.9878330230713, 12.4962501525879, 17.7259578704834, 30.9099159240723, >>>>> 25.4832077026367), value610 = c(23.4706859588623, 17.0126209259033, >>>>> 26.8166942596436, 15.297459602356, 25.1733055114746, 23.5616931915283, >>>>> 8.86995983123779, 13.5793552398682, 27.5732250213623, 22.1691932678223 >>>>> ), value611 = c(14.5820417404175, 9.08279132843018, 17.8419170379639, >>>>> 8.36016654968262, 16.5633754730225, 14.8123331069946, 1.32095837593079, >>>>> 5.73408317565918, 18.9752082824707, 13.5729999542236), value612 = >>>>> c(9.12979793548584, >>>>> 2.79943537712097, 11.6504030227661, 2.21584677696228, 10.5404834747314, >>>>> 7.55471754074097, -5.58141136169434, -0.566209673881531, >>>>> 12.3264112472534, >>>>> 6.65576601028442)), .Names = c("value601", "value602", "value603", >>>>> "value604", "value605", "value606", "value607", "value608", "value609", >>>>> "value610", "value611", "value612"), row.names = c("1", "2", >>>>> "3", "4", "5", "6", "7", "8", "9", "10"), class = "data.frame") >>>>> >>>>> [[alternative HTML version deleted]] >>>>> >>>>> ______________________________________________ >>>>> R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see >>>>> https://stat.ethz.ch/mailman/listinfo/r-help >>>>> PLEASE do read the posting guide http://www.R-project.org/posti >>>>> ng-guide.html >>>>> and provide commented, minimal, self-contained, reproducible code. >>>>> >>>>> >>>> >>>> >>>> -- >>>> Dan Dalthorp, PhD >>>> USGS Forest and Rangeland Ecosystem Science Center >>>> Forest Sciences Lab, Rm 189 >>>> 3200 SW Jefferson Way >>>> Corvallis, OR 97331 >>>> ph: 541-750-0953 >>>> ddalth...@usgs.gov >>>> >>>> >>> >>> [[alternative HTML version deleted]] >>> >>> ______________________________________________ >>> R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see >>> 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. >> >> >> ______________________________________________ >> R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see >> 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. >> > ______________________________________________ R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see 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.