I think you want to use a single `&' rather than a double `&&'.
-roger
HENRIKSON, JEFFREY wrote:
I would like to know if there is a way to do the following command in one step, primarily for speed on large data (5 million elements), and secondarily for readablity.
mean(delta[(intersect(which(x[['class']]==0),which(delta<1)))])
Do I really have to rely on an intersect operator? Isn't that O(nlg(n))? Can't I just filter in one step? As an R newbie, I would have guessed I could write
mean(delta[which((x[['class']]==0) && (delta<1))])
But I guess no such luck since (delta<1), etc are vectors. Are they really implemented as vectors? Ie, if I take 5M data points, does it allocate 20MB of RAM to make a test that passes most of the elements?
The only thing I can think of is to use closures to write something like a Lisp list "filter". Not sure on the readabilty merits, especially if there is a direct way to do it. If Matlab had closures I know running them in a loop would be a bear on runtime anyway.
Jeff Henrikson
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