On Apr 30, 2010, at 6:59 AM, Mohamed Lajnef wrote:
Hi Soeren
Apply or aggregate functions
Probably needs combn as well. Could do it all with numeric indices,
but this effort with character vectors seems acceptable:
fun <- function(x){ cnms <- colnames(x)
return(apply(combn(cnms,2), 2, function(y) sum(x[,y])))
}
fun(df)
#[1] 210 310 410
I do have a question about "returning a matrix" though. Did you mena
that you wanted the pairs of sums rather than the sums of pairs. In
that case:
fun2 <- function(x){cnms <- colnames(x)
return(apply(combn(cnms,2), c(1,2), function(y) sum(x[,y])))
}
fun2(df)
# [,1] [,2] [,3]
#[1,] 55 55 155
#[2,] 155 255 255
--
David.
best regards
M
soeren.vo...@eawag.ch a écrit :
Hello, a data.frame, df, holds the numerics, x, y, and z. A
function, fun, should return some arbitrary statistics about the
arguments, e.g. the sum or anything else. What I want to do is to
apply this function to every pair of variables in df, and the
return should be a matrix as found with cov. How can I achieve
that? Thanks, Sören
df <- data.frame(x=1:10, y=11:20, z=21:30);
fun <- function(x){
return(sum(x));
}
# and now???
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--
Mohamed Lajnef,IE INSERM U955 eq 15
Pôle de Psychiatrie
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94010 CRETEIL Cedex FRANCE
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fax : 01 49 81 30 99
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David Winsemius, MD
West Hartford, CT
______________________________________________
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