R help - Oct 2007 - Calculating group means using self-written function

Hi R-users,

Suppose I have a following data set.

y1 <- rnorm(20) + 6.8
y2 <- rnorm(20) + (1:20*1.7 + 1)
y3 <- rnorm(20) + (1:20*6.7 + 3.7)
y <- c(y1,y2,y3)
var1 <- rep(1:5,12)
z <- rep(1:6,10)
f <- gl(3,20, labels=paste("lev", 1:3, sep=""))
d <- data.frame(var1=var1, z=z,y=y, f=f)

Using following code I can calculate group means

library(doBy)
summaryBy(y ~ f + var1, data=d, FUN=mean)

How do I have to modify the FUN argument if I want to calculate mean
using unique values

for instance

fun <- function(x, y) sum(x)/length(unique(y))
summaryBy(y ~ f + var1, data=d, FUN=fun(y, z)

Error in get(x, envir, mode, inherits) : variable "currFUN" of mode
"function" was not found

Best regards
LN

Hi

r-help-bounces at r-project.org napsal dne 02.10.2007 10:44:20:
> Hi R-users,
> 
> Suppose I have a following data set.
> 
> y1 <- rnorm(20) + 6.8
> y2 <- rnorm(20) + (1:20*1.7 + 1)
> y3 <- rnorm(20) + (1:20*6.7 + 3.7)
> y <- c(y1,y2,y3)
> var1 <- rep(1:5,12)
> z <- rep(1:6,10)
> f <- gl(3,20, labels=paste("lev", 1:3, sep=""))
> d <- data.frame(var1=var1, z=z,y=y, f=f)
> 
> Using following code I can calculate group means
> 
> library(doBy)
> summaryBy(y ~ f + var1, data=d, FUN=mean)
> 
> How do I have to modify the FUN argument if I want to calculate mean
> using unique values
> 
> for instance
> 
> fun <- function(x, y) sum(x)/length(unique(y))
> summaryBy(y ~ f + var1, data=d, FUN=fun(y, z)
> 
> Error in get(x, envir, mode, inherits) : variable "currFUN" of
mode
> "function" was not found
Not sure how to do it in doBy but using aggregate

aggregate(d$y, list(d$var1,d$f), fun, y=z)

probably do what you want

Regards
Petr
> 
> Best regards
> LN
> 
> ______________________________________________
> 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.

Lauri Nikkinen wrote:
> 
> Suppose I have a following data set.
> 
> y1 <- rnorm(20) + 6.8
> y2 <- rnorm(20) + (1:20*1.7 + 1)
> y3 <- rnorm(20) + (1:20*6.7 + 3.7)
> y <- c(y1,y2,y3)
> var1 <- rep(1:5,12)
> z <- rep(1:6,10)
> f <- gl(3,20, labels=paste("lev", 1:3, sep=""))
> d <- data.frame(var1=var1, z=z,y=y, f=f)
> 
> Using following code I can calculate group means
> 
> library(doBy)
> summaryBy(y ~ f + var1, data=d, FUN=mean)
> 
> How do I have to modify the FUN argument if I want to calculate mean
> using unique values
> 
> for instance
> 
> fun <- function(x, y) sum(x)/length(unique(y))
> summaryBy(y ~ f + var1, data=d, FUN=fun(y, z)
> 
> Error in get(x, envir, mode, inherits) : variable "currFUN" of
mode
> "function" was not found
> 
> Best regards
> LN
> 
Your first call to summaryBy suggests, that the argument FUN must be a name
of a function.
fun(y,z) in the second call is evaluated before call to summaryBy.

fun(y,z) returns a single number, so you have 
summaryBy(y ~ f + var1, data=d, FUN=331.9017)

summaryBy wants to call FUN(x) and use its result and check if it is valid. 
It cannot call 331.9017 and gives the error.

Probably, you might want to change your code for something like following

fun <- function(x, y=1) sum(x)/length(unique(y))
summaryBy(y ~ f + var1, data=d, FUN=fun, y=z)

More details should be given in ?summaryBy
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