[R] Calculating group means using self-written function

[Petr PIKAL]

Hi

lauri.nikkinen at gmail.com napsal dne 02.10.2007 13:19:09:

> Thanks Petr,
> 
> Yes, your code seems to work. But when I try to reproduce it with my
> original data set
> 
> fun <- function(x, y) sum(x)/length(unique(y))
> aggregate(vsid$lev, list(vsid$month, vsid$yeari), fun, 
vsid$lev=vsid$date)

Shall be

aggregate(vsid$lev, list(vsid$month, vsid$yeari), fun, y=vsid$date)

>From help page

## S3 method for class 'data.frame':
aggregate(x, by, FUN, ...)

...
further arguments passed to or used by methods.

Your function has 2 arguments one is x which is assigned vsid$lev and the 
other is y which you want to assign vsid$date. You can imagine that 
aggregate splits your "x" according to the levels mentioned in "by" and 
applies to each split a function "fun" together with any other argument, 
in your case "y". So you need to provide a correct name to your function 
otherwise it does not know what to do.

Regards
Petr

> 
> I get
> 
> Error: syntax error, unexpected EQ_ASSIGN, expecting ',' in
> "aggregate(vsid$lev, list(vsid$month, vsid$year), fun, vsid$lev="
> 
> Can you intepret what is wrong? vsid$date is
> 
> $ date       :Class 'Date'  num [1:637] 13695 13695 13695 13695 13695 
...
> 
> Cheers,
> Lauri
> 
> 2007/10/2, Petr PIKAL <petr.pikal at precheza.cz>:
> > 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.
> >
> >