# [R] Calculating group means using self-written function

Lauri Nikkinen lauri.nikkinen at iki.fi
Tue Oct 2 13:19:09 CEST 2007

```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)

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
>
> 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
> >
> > ______________________________________________
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