When I run by, I get an error message and no results. Any help in understanding what is wrong would be appreciated. Error message: Warning messages: 1: In mean.default(data[x, , drop = FALSE], ...) : argument is not numeric or logical: returning NA 2: In mean.default(data[x, , drop = FALSE], ...) : argument is not numeric or logical: returning NA
Results: Arm: MUFA [1] NA ----------------------------------------------------------------------------------------------------------------------- Arm: PUFA [1] NA Code: by(hold,Arm,mean,na.rm=TRUE) I don't understand why I am getting the error message, and why I am not getting any results. I don't believe my data are non-numeric. BY str works fine and confirms that the data are numeric > by(hold,Arm,str) 'data.frame': 23 obs. of 3 variables: $ Wtscr: num 97.2 103.9 58.2 130.9 135 ... $ Wt0 : num 96.2 106.1 56.7 127.4 133.1 ... $ Wt6 : num 93.8 101.7 55.5 127.6 130.9 ... 'data.frame': 16 obs. of 3 variables: $ Wtscr: num 120.2 104.6 100.1 74.8 112.6 ... $ Wt0 : num 117.2 105.3 99.5 75.7 110.7 ... $ Wt6 : num 114.6 104.8 84.5 77.7 107.4 ... Here is a listing of my data: > hold Wtscr Wt0 Wt6 1 120.2 117.2 114.60 2 104.6 105.3 104.80 3 97.2 96.2 93.80 4 103.9 106.1 101.70 5 58.2 56.7 55.50 6 130.9 127.4 127.60 7 135.0 133.1 130.90 8 100.1 99.5 84.50 9 130.3 115.3 115.80 10 150.5 148.7 133.40 11 74.8 75.7 77.70 12 112.6 110.7 107.40 13 90.0 91.0 83.40 14 139.1 138.5 126.70 15 99.1 96.4 95.70 16 108.3 107.5 109.30 17 75.1 72.9 72.20 18 97.5 102.1 98.50 19 202.2 90.1 90.60 20 91.7 89.4 93.40 21 102.1 102.2 100.80 22 116.9 118.9 118.00 23 94.6 95.3 90.30 24 122.2 117.0 117.00 25 105.6 103.3 103.60 26 96.9 96.8 98.80 27 102.9 100.3 89.00 28 115.8 118.5 117.30 29 95.7 96.2 95.40 30 88.2 86.9 88.30 31 108.7 108.8 108.80 32 89.2 88.6 81.20 33 86.8 86.5 82.70 34 135.5 130.1 125.40 35 112.5 113.9 111.45 36 111.0 105.3 109.50 37 103.4 100.5 95.50 38 117.6 117.4 101.40 39 116.7 118.5 101.80 The INDEX is clearly a factor: > Arm [1] PUFA PUFA MUFA MUFA MUFA MUFA MUFA PUFA MUFA MUFA PUFA PUFA PUFA MUFA MUFA PUFA PUFA PUFA MUFA MUFA MUFA MUFA MUFA PUFA MUFA MUFA PUFA MUFA PUFA MUFA PUFA [32] MUFA MUFA MUFA MUFA MUFA PUFA PUFA PUFA Levels: MUFA PUFA The data and the index have the same length: > cbind(hold,Arm) Wtscr Wt0 Wt6 Arm 1 120.2 117.2 114.60 PUFA 2 104.6 105.3 104.80 PUFA 3 97.2 96.2 93.80 MUFA 4 103.9 106.1 101.70 MUFA 5 58.2 56.7 55.50 MUFA 6 130.9 127.4 127.60 MUFA 7 135.0 133.1 130.90 MUFA 8 100.1 99.5 84.50 PUFA 9 130.3 115.3 115.80 MUFA 10 150.5 148.7 133.40 MUFA 11 74.8 75.7 77.70 PUFA 12 112.6 110.7 107.40 PUFA 13 90.0 91.0 83.40 PUFA 14 139.1 138.5 126.70 MUFA 15 99.1 96.4 95.70 MUFA 16 108.3 107.5 109.30 PUFA 17 75.1 72.9 72.20 PUFA 18 97.5 102.1 98.50 PUFA 19 202.2 90.1 90.60 MUFA 20 91.7 89.4 93.40 MUFA 21 102.1 102.2 100.80 MUFA 22 116.9 118.9 118.00 MUFA 23 94.6 95.3 90.30 MUFA 24 122.2 117.0 117.00 PUFA 25 105.6 103.3 103.60 MUFA 26 96.9 96.8 98.80 MUFA 27 102.9 100.3 89.00 PUFA 28 115.8 118.5 117.30 MUFA 29 95.7 96.2 95.40 PUFA 30 88.2 86.9 88.30 MUFA 31 108.7 108.8 108.80 PUFA 32 89.2 88.6 81.20 MUFA 33 86.8 86.5 82.70 MUFA 34 135.5 130.1 125.40 MUFA 35 112.5 113.9 111.45 MUFA 36 111.0 105.3 109.50 MUFA 37 103.4 100.5 95.50 PUFA 38 117.6 117.4 101.40 PUFA 39 116.7 118.5 101.80 PUFA But the by function does not work! > by(hold,Arm,mean,na.rm=TRUE) Arm: MUFA [1] NA ----------------------------------------------------------------------------------------------------------------------- Arm: PUFA [1] NA Warning messages: 1: In mean.default(data[x, , drop = FALSE], ...) : argument is not numeric or logical: returning NA 2: In mean.default(data[x, , drop = FALSE], ...) : argument is not numeric or logical: returning NA Perhaps this is a hint, print does not give two separate group: > by(hold,Arm,print) Wtscr Wt0 Wt6 3 97.2 96.2 93.80 4 103.9 106.1 101.70 5 58.2 56.7 55.50 6 130.9 127.4 127.60 7 135.0 133.1 130.90 9 130.3 115.3 115.80 10 150.5 148.7 133.40 14 139.1 138.5 126.70 15 99.1 96.4 95.70 19 202.2 90.1 90.60 20 91.7 89.4 93.40 21 102.1 102.2 100.80 22 116.9 118.9 118.00 23 94.6 95.3 90.30 25 105.6 103.3 103.60 26 96.9 96.8 98.80 28 115.8 118.5 117.30 30 88.2 86.9 88.30 32 89.2 88.6 81.20 33 86.8 86.5 82.70 34 135.5 130.1 125.40 35 112.5 113.9 111.45 36 111.0 105.3 109.50 Wtscr Wt0 Wt6 1 120.2 117.2 114.6 2 104.6 105.3 104.8 8 100.1 99.5 84.5 11 74.8 75.7 77.7 12 112.6 110.7 107.4 13 90.0 91.0 83.4 16 108.3 107.5 109.3 17 75.1 72.9 72.2 18 97.5 102.1 98.5 24 122.2 117.0 117.0 27 102.9 100.3 89.0 29 95.7 96.2 95.4 31 108.7 108.8 108.8 37 103.4 100.5 95.5 38 117.6 117.4 101.4 39 116.7 118.5 101.8 Arm: MUFA Wtscr Wt0 Wt6 3 97.2 96.2 93.80 4 103.9 106.1 101.70 5 58.2 56.7 55.50 6 130.9 127.4 127.60 7 135.0 133.1 130.90 9 130.3 115.3 115.80 10 150.5 148.7 133.40 14 139.1 138.5 126.70 15 99.1 96.4 95.70 19 202.2 90.1 90.60 20 91.7 89.4 93.40 21 102.1 102.2 100.80 22 116.9 118.9 118.00 23 94.6 95.3 90.30 25 105.6 103.3 103.60 26 96.9 96.8 98.80 28 115.8 118.5 117.30 30 88.2 86.9 88.30 32 89.2 88.6 81.20 33 86.8 86.5 82.70 34 135.5 130.1 125.40 35 112.5 113.9 111.45 36 111.0 105.3 109.50 ----------------------------------------------------------------------------------------------------------------------- Arm: PUFA Wtscr Wt0 Wt6 1 120.2 117.2 114.6 2 104.6 105.3 104.8 8 100.1 99.5 84.5 11 74.8 75.7 77.7 12 112.6 110.7 107.4 13 90.0 91.0 83.4 16 108.3 107.5 109.3 17 75.1 72.9 72.2 18 97.5 102.1 98.5 24 122.2 117.0 117.0 27 102.9 100.3 89.0 29 95.7 96.2 95.4 31 108.7 108.8 108.8 37 103.4 100.5 95.5 38 117.6 117.4 101.4 39 116.7 118.5 101.8 But summary works as expected, giving two groups of results! > by(hold,Arm,summary) Arm: MUFA Wtscr Wt0 Wt6 Min. : 58.20 Min. : 56.7 Min. : 55.5 1st Qu.: 95.75 1st Qu.: 92.7 1st Qu.: 92.0 Median :105.60 Median :103.3 Median :101.7 Mean :112.75 Mean :106.3 Mean :104.0 3rd Qu.:130.60 3rd Qu.:118.7 3rd Qu.:117.7 Max. :202.20 Max. :148.7 Max. :133.4 ----------------------------------------------------------------------------------------------------------------------- Arm: PUFA Wtscr Wt0 Wt6 Min. : 74.80 Min. : 72.90 Min. : 72.20 1st Qu.: 97.05 1st Qu.: 98.67 1st Qu.: 87.88 Median :104.00 Median :103.70 Median : 99.95 Mean :103.15 Mean :102.54 Mean : 97.58 3rd Qu.:113.62 3rd Qu.:112.28 3rd Qu.:107.75 Max. :122.20 Max. :118.50 Max. :117.00 BY also shows that there are no NAs in the data, and the BY works properly. > by(hold,Arm,is.na) Arm: MUFA Wtscr John David Sorkin M.D., Ph.D. Professor of Medicine Chief, Biostatistics and Informatics University of Maryland School of Medicine Division of Gerontology and Geriatric Medicine Baltimore VA Medical Center 10 North Greene Street GRECC (BT/18/GR) Baltimore, MD 21201-1524 (Phone) 410-605-7119 (Fax) 410-605-7913 (Please call phone number above prior to faxing) Confidentiality Statement: This email message, including any attachments, is for the sole use of the intended recipient(s) and may contain confidential and privileged information. Any unauthorized use, disclosure or distribution is prohibited. If you are not the intended recipient, please contact the sender by reply email and destroy all copies of the original message. ______________________________________________ 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.