f some data and an aching desire for an answer does not
> ensure that a reasonable answer can be extracted from a given body of data.
> ~ John Tukey
>
> -Oorspronkelijk bericht-
> Van: Bert Gunter [mailto:gunter.ber...@gene.com]
> Verzonden: maandag 5 november 2012 16:13
> Aan:
ey
-Oorspronkelijk bericht-
Van: Bert Gunter [mailto:gunter.ber...@gene.com]
Verzonden: maandag 5 november 2012 16:13
Aan: D. Rizopoulos
CC: ONKELINX, Thierry; r-help@r-project.org
Onderwerp: Re: [R] averaging a list of matrices element wise
Gents:
Although it is difficult to say what may be
Gents:
Well... (munch munch) I do think I must eat my words:
>z <- lapply(seq_len(1e6),function(x)matrix(runif(100),nr=10))
> system.time(Reduce("+",z)/length(z))
user system elapsed
3.480.053.52
> system.time(rowMeans(array(unlist(z),dim=c(10,10,length(z))),dims=2))
user syst
Gents:
Although it is difficult to say what may be faster, as it typically
depends on the data, and it is even more difficult to say what is
fast enough, I suspect that
?rowMeans ## specifically written for speed
would be considerably faster than Reduce (or an apply() )approach on
the array), b
"r-help@r-project.org"
Cc:
Sent: Monday, November 5, 2012 5:32 AM
Subject: [R] averaging a list of matrices element wise
Dear all,
I have a list of n matrices which all have the same dimension (r x s). What
would be a fast/elegant way to calculate the element wise average? So result[1,
1] <
If you don't have any NAs, then one way is:
n <- 3
r <- 5
s <- 6
raw <- lapply(seq_len(n), function(i){
matrix(rnorm(r * s), ncol = r)
})
Reduce("+", raw) / length(raw)
I hope it helps.
Best,
Dimitris
On 11/5/2012 11:32 AM, ONKELINX, Thierry wrote:
> Dear all,
>
> I have a list of n matri
Dear all,
I have a list of n matrices which all have the same dimension (r x s). What
would be a fast/elegant way to calculate the element wise average? So result[1,
1] <- mean(c(raw[[1]][1, 1] , raw[[2]][1, 1], raw[[...]][1, 1], raw[[n]][1, 1]))
Here is my attempt.
#create a dummy dataset
n <
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