Hi.
There is no need to do this in a for loop.
Here is one approach:
x <- read.table(textConnection("Site Prof H
1 1 24
1 1 16
1 1 67
1 2 23
1 2 56
1 2 45
2 1 67
2 1 46"), header = TRUE)
closeAllConnections()
x
cbind(x,newCol=unlist(tapply(x[,3],paste(x[,1],x[,2],sep=""),
function(x) x-min(x)))
Site Prof H newCol
111 1 1 24 8
112 1 1 16 0
113 1 1 67 51
121 1 2 23 0
122 1 2 56 33
123 1 2 45 22
211 2 1 67 21
212 2 1 46 0
Andrija
On Tue, May 3, 2011 at 5:44 PM, Woida71 <w.gost...@ipp.bz.it> wrote:
> Hello everybody,
> I am beginning with loops and functions and would be glad to have help in
> the following question:
> If i have a dataframe like this
> Site Prof H
> 1 1 24
> 1 1 16
> 1 1 67
> 1 2 23
> 1 2 56
> 1 2 45
> 2 1 67
> 2 1 46
> And I would like to create a new column that subtracts the minimum of H
> from
> H, but for S1 and P1
> only the minimum of the data points falling into this category should be
> taken.
> So for example the three first numbers of the new column write: 24-16,
> 16-16, 67-16
> the following numbers refering to Site1 and Prof2 write: 23-23, 56-23,
> 45-23.
> I think with two loops one refering to the Site, the other to the Prof, it
> should be possible to automatically
> create the new column.
> Thanks a lot for any help.
>
> --
> View this message in context:
> http://r.789695.n4.nabble.com/Simple-loop-tp3492819p3492819.html
> Sent from the R help mailing list archive at Nabble.com.
>
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