Hi David, Once again, thanks for your help. I still need some help. My original post was quite simplified, and perhaps that was a mistake.
Here is the actual code and screen output from R: # Set the working directory setwd("C:\\Documents and Settings\\jfloren\\My Documents\\TestRSoil") # Read from the table generated in step 1 labinfo <- read.table(file = "./TableTestSoil1-25-10.txt", header = TRUE, sep = "\t") attach(labinfo) soil = data.frame(NAPT_ID, Date_Recd, Soil, Primary_A, Anlysis, Anlysis_Soil, Unit, Results, count, minall, maxall, amed, rndmedian, aMAD, rndMAD, rndNoF, rndm4, rndm2, rndp2, rndp4, rndavg, rndsd) detach(labinfo) attach(soil) # NOTE: Here is the soil data frame. This is from another table that has already calculated the median, Median Absolute Deviation (MAD), and the -4.0 MAD to + 4.0 MAD values: > > str(soil) 'data.frame': 9563 obs. of 22 variables: $ NAPT_ID : Factor w/ 27 levels "13003","14001",..: 26 16 25 12 9 5 17 14 20 19 ... $ Date_Recd : Factor w/ 46 levels "1/0/00","10/15/2008",..: 9 9 9 2 10 3 7 11 9 12 ... $ Soil : Factor w/ 21 levels "2008-116","2008-117",..: 1 1 1 1 1 1 1 1 1 1 ... $ Primary_A : Factor w/ 9 levels "Bases","Buffer pH, Lime Req.",..: 1 1 1 1 1 1 1 1 1 1 ... $ Anlysis : Factor w/ 32 levels "Anlysis","B",..: 5 5 5 5 5 5 5 5 5 5 ... $ Anlysis_Soil: Factor w/ 611 levels "Anlysis_Soil",..: 2 2 2 2 2 2 2 2 2 2 ... $ Unit : Factor w/ 4 levels "%","(dS/m)","mg/kg",..: 3 3 3 3 3 3 3 3 3 3 ... $ Results : Factor w/ 3796 levels "0.05","0.06",..: 887 456 567 574 575 603 614 626 627 641 ... $ count : Factor w/ 19 levels "10","11","12",..: 12 12 12 12 12 12 12 12 12 12 ... $ minall : Factor w/ 477 levels "0.05","0.06",..: 150 150 150 150 150 150 150 150 150 150 ... $ maxall : Factor w/ 516 levels "0.12","0.17",..: 115 115 115 115 115 115 115 115 115 115 ... $ amed : Factor w/ 552 levels "0.1","0.105",..: 133 133 133 133 133 133 133 133 133 133 ... $ rndmedian : Factor w/ 531 levels "0.1","0.11","0.13",..: 122 122 122 122 122 122 122 122 122 122 ... $ aMAD : Factor w/ 433 levels "0.00499999999999989",..: 193 193 193 193 193 193 193 193 193 193 ... $ rndMAD : Factor w/ 341 levels "0","0.01","0.02",..: 107 107 107 107 107 107 107 107 107 107 ... $ rndNoF : Factor w/ 335 levels "0.2","0.9","1",..: 108 108 108 108 108 108 108 108 108 108 ... $ rndm4 : Factor w/ 537 levels "-0.04","-0.05",..: 533 533 533 533 533 533 533 533 533 533 ... $ rndm2 : Factor w/ 529 levels "-0.04","-0.1",..: 126 126 126 126 126 126 126 126 126 126 ... $ rndp2 : Factor w/ 554 levels "0.13","0.14",..: 143 143 143 143 143 143 143 143 143 143 ... $ rndp4 : Factor w/ 545 levels "0.15","0.16",..: 151 151 151 151 151 151 151 151 151 151 ... $ rndavg : Factor w/ 561 levels "0.1","0.11","0.13",..: 127 127 127 127 127 127 127 127 127 127 ... $ rndsd : Factor w/ 416 levels "0.02","0.03",..: 256 256 256 256 256 256 256 256 256 256 ... > # NOTE: Original posting -4MAD is rndm4 (col 17); -2.5MAD is rndm2 (col 18); +2.5MAD is rndp2 (col 19); +4MAD is rndp4 (col 20). I changed the columns to 17:18 in the following as.numeric code you supplied: > > df.soil$a_flag <- apply(df.soil, 1, function(.x) + switch(findInterval(.x[3], as.numeric( c(-Inf,.x[17:20],Inf)) ), + "**L", "*L", " ", "*H", + "**H") ) Error in apply(df.soil, 1, function(.x) switch(findInterval(.x[3], as.numeric(c(-Inf, : object 'df.soil' not found > # End of R code with the error message "object 'df.soil' not found" I also thought that perhaps "df.soil" was an abbreviation for "data.frame.soil" However, with either "df.soil" or "data.frame.soil", R sends the error message, "object 'df.soil' ('data.frame.soil') not found." Are you able to see what I am doing wrong? Thanks, Jerry Floren Minnesota Department of Agriculture -- View this message in context: http://n4.nabble.com/Comparing-Variables-and-Writing-a-New-Column-tp1458947p1459112.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.