Hi, I have yield data for several varieties and a randomly placed check (1 in every 8 column or "cols") in a field test arranged in a rows*cols grid format (see image attached). Both "rows" & "cols" are variables in the data set. I like to adjust "yield" variable for each row listed as "variety" in variable "linecode" by dividing its yield with the average yield of four nearest "check" (on the rows*cols field grid) in variable "linecode". I like to have two checks on the same row where one check is on the left and the other is on the right side of a given variety. The other two checks should come from the two neighboring columns ("cols"). If a check is missing on one or more sides of a given variety, then I like to proceed with the calculation with only the available checks around that given variety. If two checks on the neighboring column are equidistance from a given variety then use position of the variety to choose which one to use (If variety is in cols 1-8 then use check from those cols; if variety is in cols 9-16 then use check from cols 9-16). Below is the function I wrote which adjust yield values for each "variety" (variable "linecode") by dividing its yield with the average yield of all checks in the field. Instead of using average check across the whole field, I like to use the four neighboring checks to make this adjustment. I am struggling with specifying the four nearest checks in this loop. I played around using "dist" function but without any success. I tried searching for any packages that can do these nearest check adjustments without any success. Any help will be appreciated. -------------------function------------------------------------------ function (dataset, trait, control) { m <- c() x <- length(trait) chkmean <- tapply(trait, control, mean, na.rm = T) for (i in 1:x) { m[i] <- ifelse(control[i] == "variety", trait[i]/chkmean[1], trait[i]/trait[i]) } head(as.data.frame(m)) } ---------------------data---------------------------------------------------------------------- dput(dat) structure(list(rows = structure(c(1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L), .Label = c("1", "2", "3", "4"), class = "factor"), cols = structure(c(1L, 2L, 3L, 4L, 5L, 6L, 7L, 8L, 9L, 10L, 11L, 12L, 13L, 14L, 15L, 16L, 16L, 15L, 14L, 13L, 12L, 11L, 10L, 9L, 8L, 7L, 6L, 5L, 4L, 3L, 2L, 1L, 1L, 2L, 3L, 4L, 5L, 6L, 7L, 8L, 9L, 10L, 11L, 12L, 13L, 14L, 15L, 16L, 16L, 15L, 14L, 13L, 12L, 11L, 10L, 9L, 8L, 7L, 6L, 5L, 4L, 3L, 2L, 1L), .Label = c("1", "2", "3", "4", "5", "6", "7", "8", "9", "10", "11", "12", "13", "14", "15", "16"), class = "factor"), plotid = c(289L, 290L, 291L, 292L, 293L, 294L, 295L, 296L, 297L, 298L, 299L, 300L, 301L, 302L, 303L, 304L, 369L, 370L, 371L, 372L, 373L, 374L, 375L, 376L, 377L, 378L, 379L, 380L, 381L, 382L, 383L, 384L, 385L, 386L, 387L, 388L, 389L, 390L, 391L, 392L, 393L, 394L, 395L, 396L, 397L, 398L, 399L, 400L, 465L, 466L, 467L, 468L, 469L, 470L, 471L, 472L, 473L, 474L, 475L, 476L, 477L, 478L, 479L, 480L), yield = c(5.1, 5.5, 5, 5.5, 6.2, 5.1, 5.5, 5.2, 5, 5, 3.9, 4.6, 5, 4.4, 5.1, 4.3, 4.4, 4.2, 3.9, 4.6, 4.8, 5.4, 4.7, 5.5, 5.3, 4.8, 5.8, 4.6, 5.8, 5.5, 5.3, 5.6, 5.6, 5, 4.8, 4.9, 5.2, 5.3, 4.6, 4.8, 5.3, 4.2, 4.6, 4.2, 4.2, 4, 3.9, 4.5, 5.4, 4.8, 4.6, 5.2, 4.9, 5.1, 4.5, 5.8, 5.2, 4.7, 4.8, 5.3, 5.8, 4.9, 5.9, 4.5), line = structure(c(1L, 2L, 3L, 4L, 5L, 6L, 7L, 8L, 9L, 1L, 10L, 11L, 12L, 13L, 14L, 15L, 16L, 17L, 18L, 19L, 20L, 1L, 21L, 22L, 1L, 23L, 24L, 25L, 26L, 27L, 28L, 29L, 30L, 31L, 32L, 33L, 1L, 34L, 35L, 36L, 37L, 38L, 39L, 40L, 41L, 42L, 1L, 43L, 44L, 45L, 46L, 47L, 48L, 49L, 50L, 1L, 51L, 52L, 53L, 54L, 1L, 55L, 56L, 57L), .Label = c("CHK", "V002", "V003", "V004", "V005", "V006", "V007", "V008", "V009", "V010", "V011", "V012", "V013", "V014", "V015", "V016", "V017", "V018", "V019", "V020", "V021", "V022", "V023", "V024", "V025", "V026", "V027", "V028", "V029", "V030", "V031", "V032", "V033", "V034", "V035", "V036", "V037", "V038", "V039", "V040", "V041", "V042", "V043", "V044", "V045", "V046", "V047", "V048", "V049", "V050", "V051", "V052", "V053", "V054", "V055", "V056", "V057" ), class = "factor"), linecode = structure(c(1L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 1L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 1L, 2L, 2L, 1L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 1L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 1L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 1L, 2L, 2L, 2L, 2L, 1L, 2L, 2L, 2L), .Label = c("check", "variety"), class = "factor")), .Names = c("rows", "cols", "plotid", "yield", "line", "linecode"), row.names = c(NA, -64L), class = "data.frame") ------------------------------------------------------------------------------------------------- My expected output is in column "adj_yield" below: rows cols plotid yield line linecode adj_yield 1 1 1 289 5.1 CHK check check 2 1 2 290 5.5 V002 variety 1.071 3 1 3 291 5.0 V003 variety 0.974 4 1 4 292 5.5 V004 variety 1.071 5 1 5 293 6.2 V005 variety 1.208 6 1 6 294 5.1 V006 variety 0.994 7 1 7 295 5.5 V007 variety 1.071 8 1 8 296 5.2 V008 variety 1.013 9 1 9 297 5.0 V009 variety 0.974 10 1 10 298 5.0 CHK check check 11 1 11 299 3.9 V010 variety 0.750 12 1 12 300 4.6 V011 variety 0.885 13 1 13 301 5.0 V012 variety 0.962 14 1 14 302 4.4 V013 variety 0.846 15 1 15 303 5.1 V014 variety 0.981 16 1 16 304 4.3 V015 variety 0.827 17 2 16 369 4.4 V016 variety check 18 2 15 370 4.2 V017 variety 0.881 19 2 14 371 3.9 V018 variety 0.818 20 2 13 372 4.6 V019 variety 0.965 21 2 12 373 4.8 V020 variety 1.007 22 2 11 374 5.4 CHK check check 23 2 10 375 4.7 V021 variety 0.959 24 2 9 376 5.5 V022 variety 1.053 25 2 8 377 5.3 CHK check check 26 2 7 378 4.8 V023 variety 0.923 27 2 6 379 5.8 V024 variety 1.115 28 2 5 380 4.6 V025 variety 0.885 29 2 4 381 5.8 V026 variety 1.115 30 2 3 382 5.5 V027 variety 1.058 31 2 2 383 5.3 V028 variety 1.019 32 2 1 384 5.6 V029 variety 1.077 -----------------session info------------------------------------------------------------------------ R version 3.2.1 (2015-06-18) Platform: i386-w64-mingw32/i386 (32-bit) Running under: Windows 7 x64 (build 7601) Service Pack 1 locale: [1] LC_COLLATE=English_United States.1252 LC_CTYPE=English_United States.1252 [3] LC_MONETARY=English_United States.1252 LC_NUMERIC=C [5] LC_TIME=English_United States.1252 attached base packages: [1] stats graphics grDevices utils datasets methods base other attached packages: [1] rlist_0.4.5.1 mapplots_1.5 agridat_1.12 loaded via a namespace (and not attached): [1] magrittr_1.5 plyr_1.8.3 tools_3.2.1 reshape2_1.4.1 Rcpp_0.12.0 stringi_0.5-5 [7] grid_3.2.1 data.table_1.9.4 stringr_1.0.0 chron_2.3-47 lattice_0.20-31 Nilesh Dighe (806)-252-7492 (Cell) (806)-741-2019 (Office) This e-mail message may contain privileged and/or confidential information, and is intended to be received only by persons entitled to receive such information. 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