[R] multivariate version of aggregate

Jannis bt_jannis at yahoo.de
Fri Jun 28 10:31:10 CEST 2013

Yes, I had a look at that function. From the documentation, however, it 
did not get clear to me how to split the dataframe into subsets of rows 
based on an index argument. Like:

testframe <- data.frame(a=rnorm(100), b = rnorm(100))
indices      <- rep(c(1,2), each = 50)

results <- ddply(.data = testframe, INDICES= indices, .fun = function(x) 
corr(x[,1], x[,2]))

Where the last command would yield the correlations between column 1 and 
2 of the first 50 and of the last 50 values.

Any ideas?


On 27.06.2013 21:43, Greg Snow wrote:
> Look at the plyr package, probably the ddply function in that package.  You
> can write your own function to do whatever you want on the pieces of the
> split apart object.  Correlation between a specified pair of columns would
> be simple.
> On Thu, Jun 27, 2013 at 11:26 AM, Jannis <bt_jannis at yahoo.de> wrote:
>> Dear List members,
>> i am seeking a multivariate version of aggregate. I want to compute, fro
>> example the correlation between subsets of two vectors. In aggregate, i can
>> only supply one vector with indices for subsets. Is  there ready function
>> for this or do i need to program my own?
>> Cheers
>> Jannis
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