[R] only 0s may be mixed with negative subscripts

[ilai]

Like this ? sum every batch of n rows?

N <- 2
t(kronecker(diag(nrow(sens2)/N),rep(1,N))) %*% as.matrix(sens2)

           Time         Y         X rownumber
[1,] 2657130134 0.3236854 0.1080725         3
[2,] 2657130134 0.4621816 0.1198302         7
[3,] 2657130134 0.4341804 0.1069583        11

Check rownumber column: 1+2 = 3, 3+4 = 7, 5+6=11 ...

Or sum every 3 rows:
 N <- 3
 t(kronecker(diag(nrow(sens2)/N),rep(1,N))) %*% as.matrix(sens2 )
           Time         Y         X rownumber
[1,] 3985695201 0.5646581 0.1693338         6
[2,] 3985695202 0.6553893 0.1655272        15

Hope this helps (more...).

On Mon, Feb 13, 2012 at 4:04 PM, Hasan Diwan <hasan.diwan at gmail.com> wrote:
> On 13 February 2012 14:46, ilai <keren at math.montana.edu> wrote:
>> The function you posted runs without error (on these 6 lines), but
>> does not return anything that looks remotely like a sum, or cumsum of
>> anything. Can you clarify what you are trying to do? I assume by "sum
>> of every other row" you don't mean summing Time, X and Y for rows
>> 1,3,5,..., ?
>
> I'm trying to get a piecewise sum of every n rows in a given column in
> this data set.
>> For the sum of sens2[c(1,3,5,...),] for every column (assuming no NA's
>> in the data) you could
>
> I do format checking well before getting to this stage in the analysis.
>>
>>  (1:nrow(sens2) %% 2) %*% as.matrix(sens2)
>
> That does not do what I want... Again, what it should return is a list
> of the sum of the current and preceding row.
> --
> Sent from my mobile device
> Envoyait de mon portable
>
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