Hi Dr Singh, The object mtcars is a data frame and the mean is not defined for a data frame. If you try it on a component of the data frame for which mean is defined:
by(mtcars$mpg,mtcars$am,mean) mtcars$am: 0 [1] 17.14737 ------------------------------------------------------------ mtcars$am: 1 [1] 24.39231 Jim On Fri, Apr 15, 2016 at 6:14 AM, Akhilesh Singh <akhileshsingh.i...@gmail.com> wrote: > Dear Sirs, > > I am Professor at Indira Gandhi Krishi Vishwavidyalaya, Raipur, > Chhattisgarh, India. > > While taking classes, I found the *by() *function producing following error > when I use FUN=mean or median and some other functions, however, > FUN=summary works. > > Given below is the output of the example I used on a built-in dataset > "mtcars", along with error message reproduced herewith: > >> by(data=mtcars, INDICES=list(mtcars$am), FUN=mean) > : 0 > [1] NA > ------------------------------------------------------------ > : 1 > [1] NA > Warning messages: > 1: In mean.default(data[x, , drop = FALSE], ...) : > argument is not numeric or logical: returning NA > 2: In mean.default(data[x, , drop = FALSE], ...) : > argument is not numeric or logical: returning NA > > However, the same by() function works for FUN=summary, given below is the > output: > >> by(data=mtcars, INDICES=list(mtcars$am), FUN=summary) > : 0 > mpg cyl disp hp > Min. :10.40 Min. :4.000 Min. :120.1 Min. : 62.0 > 1st Qu.:14.95 1st Qu.:6.000 1st Qu.:196.3 1st Qu.:116.5 > Median :17.30 Median :8.000 Median :275.8 Median :175.0 > Mean :17.15 Mean :6.947 Mean :290.4 Mean :160.3 > 3rd Qu.:19.20 3rd Qu.:8.000 3rd Qu.:360.0 3rd Qu.:192.5 > Max. :24.40 Max. :8.000 Max. :472.0 Max. :245.0 > drat wt qsec vs am > > Min. :2.760 Min. :2.465 Min. :15.41 Min. :0.0000 Min. :0 > > 1st Qu.:3.070 1st Qu.:3.438 1st Qu.:17.18 1st Qu.:0.0000 1st Qu.:0 > > Median :3.150 Median :3.520 Median :17.82 Median :0.0000 Median :0 > > Mean :3.286 Mean :3.769 Mean :18.18 Mean :0.3684 Mean :0 > > 3rd Qu.:3.695 3rd Qu.:3.842 3rd Qu.:19.17 3rd Qu.:1.0000 3rd Qu.:0 > > Max. :3.920 Max. :5.424 Max. :22.90 Max. :1.0000 Max. :0 > > gear carb > Min. :3.000 Min. :1.000 > 1st Qu.:3.000 1st Qu.:2.000 > Median :3.000 Median :3.000 > Mean :3.211 Mean :2.737 > 3rd Qu.:3.000 3rd Qu.:4.000 > Max. :4.000 Max. :4.000 > ------------------------------------------------------------ > : 1 > mpg cyl disp hp drat > > Min. :15.00 Min. :4.000 Min. : 71.1 Min. : 52.0 Min. > :3.54 > 1st Qu.:21.00 1st Qu.:4.000 1st Qu.: 79.0 1st Qu.: 66.0 1st > Qu.:3.85 > Median :22.80 Median :4.000 Median :120.3 Median :109.0 Median > :4.08 > Mean :24.39 Mean :5.077 Mean :143.5 Mean :126.8 Mean > :4.05 > 3rd Qu.:30.40 3rd Qu.:6.000 3rd Qu.:160.0 3rd Qu.:113.0 3rd > Qu.:4.22 > Max. :33.90 Max. :8.000 Max. :351.0 Max. :335.0 Max. > :4.93 > wt qsec vs am gear > > Min. :1.513 Min. :14.50 Min. :0.0000 Min. :1 Min. :4.000 > > 1st Qu.:1.935 1st Qu.:16.46 1st Qu.:0.0000 1st Qu.:1 1st Qu.:4.000 > > Median :2.320 Median :17.02 Median :1.0000 Median :1 Median :4.000 > > Mean :2.411 Mean :17.36 Mean :0.5385 Mean :1 Mean :4.385 > > 3rd Qu.:2.780 3rd Qu.:18.61 3rd Qu.:1.0000 3rd Qu.:1 3rd Qu.:5.000 > > Max. :3.570 Max. :19.90 Max. :1.0000 Max. :1 Max. :5.000 > > carb > Min. :1.000 > 1st Qu.:1.000 > Median :2.000 > Mean :2.923 > 3rd Qu.:4.000 > Max. :8.000 >> > > I am using the latest version of *R-3.2.4 on Windows*, however, this error > is being generated in the previous version too, > > Hope this reporting will get serious attention in debugging. > > With best regards, > > Dr. A.K. Singh > Head, Department of Agril. Statistics > Indira Gandhi Krishi Vishwavidyalaya, Raipur > Chhattisgarh, India, PIN-492012 > Mobile: +919752620740 > Email: akhileshsingh.i...@gmail.com > > [[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.
