[EMAIL PROTECTED] writes:
> Full_Name: jarek tuszynski
> Version: 1.8.1
> OS: windows 2000
> Submission from: (NULL) (198.151.13.10)
>
>
> Example code:
> > a=array(1:27, c(3,3,3))
> > apply(a,2, var)
> [,1] [,2] [,3]
> [1,] 1 1 1
> [2,] 1 1 1
> [3,] 1 1 1
> [4,] 1 1 1
> [5,] 1 1 1
> [6,] 1 1 1
> [7,] 1 1 1
> [8,] 1 1 1
> [9,] 1 1 1
> > apply(a,2, mean)
> [1] 11 14 17
> > apply(a,2, sd)
> [,1] [,2] [,3]
> [1,] 1 1 1
> [2,] 1 1 1
> [3,] 1 1 1
>
> I could not figure out from the documentation how MARGIN argument of function
> "apply" works in case of arrays with dimentions larger than 2, so I created the
> above test code. I still do not know how it suppose to work but I should not get
> the results with different dimentions, while calculating var and sd.
All in accordance with documentation, i.e. no bug. The fundamental
issue is that
> mean(a[,3,])
[1] 17
> var(a[,3,])
[,1] [,2] [,3]
[1,] 1 1 1
[2,] 1 1 1
[3,] 1 1 1
> sd(a[,3,])
[1] 1 1 1
In particular, var() gives a covariance matrix, but there's no such
thing as an sd() matrix, so you get the columnwise sd().
--
O__ ---- Peter Dalgaard Blegdamsvej 3
c/ /'_ --- Dept. of Biostatistics 2200 Cph. N
(*) \(*) -- University of Copenhagen Denmark Ph: (+45) 35327918
~~~~~~~~~~ - ([EMAIL PROTECTED]) FAX: (+45) 35327907
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