try this:
lapply(split(dat, dat$country), function (x) {
pres.test(x$pop1995, x$pop2000)
})
I hope it helps.
Best,
Dimitris
Corey Sparks wrote:
Dear list,
I have the function (as a simple example, which is actually part of a
larger function)
pres.test<-function(N0=N0, N1=N1)
{
dt<-5
r<-log(N1/N0)/dt
r
}
which calculates the annual growth rates in a population
Where N0 is the population classified into age intervals, say 5 years,
at time=1995, and N1 is the population by 5 year age classes at time=2000.
For example some data like this are:
country pop1995 pop2000
1 1712 1940
1 1329 1535
1 1101 1268
1 911 1048
1 758 859
2 627 710
2 513 584
2 420 475
2 754 965
2 638 741
I want to use the tapply function to apply the pres.test function over
all countries in my data table (the real data have ~150 countries and 10
age classes), but I can't seem to get tapply to take as input to FUN
more than one variable, for example I tried:
popdat<-cbind(dat2.sub$pop1995, dat2.sub$pop2000) #try to force the two
time points into a vector form
tapply(popdat, dat2.sub$country, pres.test, ...=list(N0=popdat[,1],
N1=popdat[,2])) #tried to pass the other arguments that pres.test needs
via ...
And got the error:
Error in tapply(popdat, dat2.sub$Country, pres.test, ... = list(N0 =
popdat[, :
arguments must have same length
I see that the function mapply will take multiple arguements, but I
don't think it will use an INDEX like tapply.
Any comments or clarification would be most appreciated.
Corey
--
Dimitris Rizopoulos
Assistant Professor
Department of Biostatistics
Erasmus Medical Center
Address: PO Box 2040, 3000 CA Rotterdam, the Netherlands
Tel: +31/(0)10/7043478
Fax: +31/(0)10/7043014
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