And how would you do this at R level?
I would use length(A) <- M, and the corresponding C function is
lengthgets.
Of course, the wasteful part is to create a far-too-long vector in the
first place, rather than growing it as needed.
On Wed, 10 Mar 2010, Saptarshi Guha wrote:
Hello,
I create a VECSXP(call it A) with size N(~ 5000), i then proceed to
fill the elements and find out I don't need to fill more than
M (M<< N).
Thus if i return A to the user's R code, he/she will see a list of
length 5K of which N-M are NULLs.
To avoid this, I create a new VECSXP B of length M and /duplicate/ the
elements of A.
Since I do this often, it appears to be wasteful, so can I
a) is there a resize function for a VECSXP?
if not
b) can i just do something like
SET_VECTOR_ELT(B,i, VECTOR_ELT(A,i)) instead of wrapping
VECTOR_ELT(A,i) inside a call to Rf_duplicate
(i will be UNPROTECTING A and B, though I will return B)
I suppose I can do (b), since B (since it is being returned) is
automatically protected and therefore all its elements will also be
protected, correct?
Thank you
Saptarshi
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