[R] another very simple loop question

[Petr Pikal]

Hi

What about some example data? I presume you could use some

apply, tapply, aggregate or similar function but without knowing what 
you **really** want to do and how your previous attempts failed it is 
hard to give any definite answer.

e.g.
mydf<-data.frame(year=sample(1:4,100,rep=T), 
student=sample(letters[1:4],100, rep=T), result=runif(100))
aggregate(mydf$result,list(year=mydf$year,student=mydf$student), 
mean)
   year student         x
1     1       a 0.4026579
2     2       a 0.4690311
...
15    3       d 0.5316301
16    4       d 0.4401949
> 

HTH
Petr



On 14 Apr 2006 at 0:09, Brian Quinif wrote:

Date sent:      	Fri, 14 Apr 2006 00:09:32 -0400
From:           	"Brian Quinif" <bquinif at gmail.com>
To:             	r-help at stat.math.ethz.ch
Subject:        	[R] another very simple loop question

> I have a dataset with 4 years of students, and normally I want to
> estimate things using each individual year, so I have a for loop as
> follows
> 
> for (i in 1:4){}
> 
> However, the only way I know how to calculate estimates using all four
> years of data is to put the estimations outside of the loop.  Is there
> anyway to make a for loop that uses all four years at once, then uses
> each individual year?
> 
> Thanks,
> 
> BQ
> 
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Petr Pikal
petr.pikal at precheza.cz