Bug in by() function which works for some FUN argument and does not work for others
You're right, but I think this fails to pinpoint the error. The problem is that FUN's argument is "applied to (usually data-frame) subsets of data," and the OP has used FUN = mean, which takes a vector (+ a few other classes), not a data frame, as argument. See ?mean Morals: 1. It is rather presumptuous to think that long used, well-tested, core R functionality like by() have bugs; a (new?) user's first thought should be to assume it is HIS error, not R's. 2. DO read the Help docs carefully. They are often terse, but usually they mean what they (appear to) say. Cheers, Bert Bert Gunter "The trouble with having an open mind is that people keep coming along and sticking things into it." -- Opus (aka Berkeley Breathed in his "Bloom County" comic strip )
On Thu, Apr 14, 2016 at 2:36 PM, Adrian Du?a <dusa.adrian at unibuc.ro> wrote:
I think you are not using the best function for what your intentions are. Try:
by(data=mtcars, INDICES=list(as.factor(mtcars$am)), FUN=colMeans)
: 0
mpg cyl disp hp drat wt
qsec vs
17.1473684 6.9473684 290.3789474 160.2631579 3.2863158 3.7688947
18.1831579 0.3684211
am gear carb
0.0000000 3.2105263 2.7368421
---------------------------------------------------------------------------
: 1
mpg cyl disp hp drat wt
qsec vs
24.3923077 5.0769231 143.5307692 126.8461538 4.0500000 2.4110000
17.3600000 0.5384615
am gear carb
1.0000000 4.3846154 2.9230769
See the difference between colMeans() and mean() in their respective help
files.
Hth,
Adrian
On Thu, Apr 14, 2016 at 11:14 PM, Akhilesh Singh <
akhileshsingh.igkv at gmail.com> wrote:
Dear Sirs, I am Professor at Indira Gandhi Krishi Vishwavidyalaya, Raipur, Chhattisgarh, India. While taking classes, I found the *by() *function producing following error when I use FUN=mean or median and some other functions, however, FUN=summary works. Given below is the output of the example I used on a built-in dataset "mtcars", along with error message reproduced herewith:
by(data=mtcars, INDICES=list(mtcars$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.igkv at gmail.com
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--
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University of Bucharest
Romanian Social Data Archive
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