Calculate geometric mean with tapply

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Hello,

You can write a function gmean and tapply it to your data.

gmean <- function(x, na.rm = FALSE){
	if(na.rm) x <- x[!is.na(x)]
	n <- length(x)
	prod(x)^(1/n)
}

tapply(data$value, data$group, gmean)

Hope this helps,

Rui Barradas

Em 25-06-2013 11:58, Shane Carey escreveu:
Hi,

I am trying to calculate the geometric mean with tapply. This is the
formula I am using:

exp(tapply(log(data$value), data$group, mean))

However, it returns the arithmetic mean. Any ideas?

Thanks

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Hm
-----Original Message-----
From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-
project.org] On Behalf Of Shane Carey
Sent: Tuesday, June 25, 2013 1:25 PM
To: Rui Barradas
Cc: r-help at r-project.org
Subject: Re: [R] Calculate geometric mean with tapply

Thanks for your help, put I've tried that and it still gives me back
the mean when I use it within tapply for some reason
can we believe it? Data, code please
set.seed(111)
x<-rnorm(10)
mean(x)
[1] -0.6690135
gmean(x)
[1] 0.4985282
tapply(vysled$gamapoml, vysled$vzorek, mean)
vz2   vz4   vz6 
341.0 343.0 332.4
tapply(vysled$gamapoml, vysled$vzorek, gmean)
vz2      vz4      vz6 
340.5418 342.6154 332.2701

I get different result for mean and gmean within tapply my data.

Regards
Petr

On Tue, Jun 25, 2013 at 12:17 PM, Rui Barradas <ruipbarradas at sapo.pt>
wrote:

Hello,

You can write a function gmean and tapply it to your data.

gmean <- function(x, na.rm = FALSE){
        if(na.rm) x <- x[!is.na(x)]
        n <- length(x)
        prod(x)^(1/n)
}

tapply(data$value, data$group, gmean)

Hope this helps,

Rui Barradas

Em 25-06-2013 11:58, Shane Carey escreveu:

 Hi,
I am trying to calculate the geometric mean with tapply. This is the
formula I am using:

exp(tapply(log(data$value), data$group, mean))

However, it returns the arithmetic mean. Any ideas?

Thanks

--
Shane

	[[alternative HTML version deleted]]

______________________________________________
R-help at r-project.org mailing list
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.
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May be this also works:

?exp(mean(log(abs(x))))
#[1] 0.4985282
A.K.

----- Original Message -----
From: PIKAL Petr <petr.pikal at precheza.cz>
To: Shane Carey <careyshan at gmail.com>
Cc: "r-help at r-project.org" <r-help at r-project.org>
Sent: Tuesday, June 25, 2013 8:50 AM
Subject: Re: [R] Calculate geometric mean with tapply

Hm
-----Original Message-----
From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-
project.org] On Behalf Of Shane Carey
Sent: Tuesday, June 25, 2013 1:25 PM
To: Rui Barradas
Cc: r-help at r-project.org
Subject: Re: [R] Calculate geometric mean with tapply

Thanks for your help, put I've tried that and it still gives me back
the mean when I use it within tapply for some reason
can we believe it? Data, code please
set.seed(111)
x<-rnorm(10)
mean(x)
[1] -0.6690135
gmean(x)
[1] 0.4985282
tapply(vysled$gamapoml, vysled$vzorek, mean)
? vz2?  vz4?  vz6 
341.0 343.0 332.4
tapply(vysled$gamapoml, vysled$vzorek, gmean)
? ?  vz2? ? ? vz4? ? ? vz6 
340.5418 342.6154 332.2701

I get different result for mean and gmean within tapply my data.

Regards
Petr

On Tue, Jun 25, 2013 at 12:17 PM, Rui Barradas <ruipbarradas at sapo.pt>
wrote:

Hello,

You can write a function gmean and tapply it to your data.

gmean <- function(x, na.rm = FALSE){
? ? ? ?  if(na.rm) x <- x[!is.na(x)]
? ? ? ?  n <- length(x)
? ? ? ?  prod(x)^(1/n)
}

tapply(data$value, data$group, gmean)

Hope this helps,

Rui Barradas

Em 25-06-2013 11:58, Shane Carey escreveu:

? Hi,
I am trying to calculate the geometric mean with tapply. This is the
formula I am using:

exp(tapply(log(data$value), data$group, mean))

However, it returns the arithmetic mean. Any ideas?

Thanks

--
Shane

??? [[alternative HTML version deleted]]

______________________________________________
R-help at r-project.org mailing list
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 at r-project.org mailing list
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.
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