[R] Can I avoid loop?

[tlorino@vet-alfort.fr]

Dear R-users,

I have a program to realize (big) simulations... I'm building a matrix, where the
number of rows is a parameter (say N) and the number of columns is fixed. All the matrix
can be completed avoiding loops... excepted one, I think: for the 12th column,
on the i-th row, I need something like

matrix[1,12]_0
for (i in 1:N)
matrix[i,12]_ifelse(matrix[i,1]>0, matrix[i-1,12] + ..., 0)

The values in the row i depends on the (i-1)th row only for the 12th column... Is it possible
to avoid a "for" loop here?

Thank you,
Tristan Lorino

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Mél. tlorino at vet-alfort.fr
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