[R] Change the index argument of a series

[Alberto Vieira Ferreira Monteiro]

This is probably very trivial - so I can't find an answer in the help files.

When I have a series x (x[1], x[2], ... x[n]) and I want to construct a
new series y (y[1], y[2], ... y[m]) such that y's are either interpolations
of the x's (when m > n) or a weighted mean (when m < n), is there
any direct function to do it?

For example, passing from 3 to 4 would be the same as multiplying
the series by the matrix:

rbind(c(3/3, 0, 0),
  c(1/3, 2/3, 0),
  c(0, 2/3, 1/3),
  c(0, 0, 3/3))

In the same way, passing from 4 to 3 would be the same as multiplying
the series by the matrix

rbind(c(3/4, 1/4, 0, 0),
  c(0, 2/4, 2/4, 0),
  c(0, 0, 1/4, 3/4))

How can I do it in a simple way?

Alberto Monteiro