[R] Mean of colMeans

[arun]

 Also, the ?colMeans() route seems to be slightly faster (in cases with no missing values).
set.seed(398)
x <- matrix(rnorm(1e4*2e4), ncol=2e4)

 system.time(res1 <- mean(colMeans(x)))
 # user  system elapsed 
 #0.227   0.000   0.227 



 system.time(res2 <- mean(x))
# user  system elapsed 
# 0.46    0.00    0.46 

all.equal(res1,res2)
#[1] TRUE

A.K.



On Wednesday, May 21, 2014 4:53 PM, Boris Steipe <boris.steipe at utoronto.ca> wrote:
Not necessarily. Missing values may base the means on unequal numbers of observation:

x <- c(1,1,1,2,NA,2)
dim(x) <- c(3,2)
cM <- colMeans(x, na.rm = TRUE, dims = 1)
mean(cM)
mean(x, na.rm = TRUE)

B.

On 2014-05-21, at 3:38 PM, Frede Aakmann Tøgersen wrote:

> Hhhhmmmmmmhhhm, but is that not the same as
> 
> mean(as.matrix(x))
> 
> ?????
> 
> Yours sincerely / Med venlig hilsen
> 
> 
> Frede Aakmann Tøgersen
> Specialist, M.Sc., Ph.D.
> Plant Performance & Modeling
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> 
>> -----Original Message-----
>> From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org]
>> On Behalf Of Sarah Goslee
>> Sent: 21. maj 2014 21:11
>> To: Kate Ignatius; r-help
>> Subject: Re: [R] Mean of colMeans
>> 
>> That would be because col is a function in base R, and thus a poor
>> choice of names for user objects. Nonetheless, it worked when I ran
>> it, but you didn't provide reproducible example so who knows.
>> 
>> R> set.seed(1)
>> R> x <- data.frame(matrix(runif(150), ncol=10))
>> R> # col is a function, so not a good name
>> R> col <- colMeans(x)
>> R> mean(col)
>> [1] 0.5119
>> 
>> It's polite to include the list on your reply.
>> 
>> Sarah
>> 
>> On Wed, May 21, 2014 at 2:50 PM, Kate Ignatius <kate.ignatius at gmail.com>
>> wrote:
>>> That didn't work: gave me the error =
>>> 
>>> [1] NA
>>> Warning message:
>>> In mean.default(col) : argument is not numeric or logical: returning NA
>>> 
>>> But writing it like: mean(colMeans(x, na.rm = TRUE, dims = 1)), worked
>>> 
>>> Thanks!
>>> 
>>> On Wed, May 21, 2014 at 2:31 PM, Sarah Goslee
>> <sarah.goslee at gmail.com> wrote:
>>>> Is
>>>> 
>>>> mean(col)
>>>> 
>>>> not what you're looking for?
>>>> 
>>>> Sarah
>>>> 
>>>> On Wed, May 21, 2014 at 2:26 PM, Kate Ignatius
>> <kate.ignatius at gmail.com> wrote:
>>>>> Hi All,
>>>>> 
>>>>> I've successfully gotten out the colMeans for 60 columns using:
>>>>> 
>>>>> col <- colMeans(x, na.rm = TRUE, dims = 1)
>>>>> 
>>>>> My next question is: is there a way of getting a mean of all the
>>>>> column means (ie a mean of a mean)?
>>>>> 
>>>>> Thanks!
>>>>> 
>> 
>> --
>> Sarah Goslee
>> http://www.functionaldiversity.org
>> 
>> ______________________________________________
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>> PLEASE do read the posting guide http://www.R-project.org/posting-
>> guide.html
>> and provide commented, minimal, self-contained, reproducible code.

> 
> ______________________________________________
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