On Sep 13, 2011, at 10:26 AM, travellina wrote:
Hi there,
I am looking for some help with a loop which uses three list()-
objects:
"sequence" has got numbers, "start" and "end" have got the begin/end
time
points which should be applied to the numbers in "sequence".
length() of all
three objects is identical, length() of vectors stored in "sequence"
is
longer than length() of "start" and "end" whose length() is
identical. Here
is an example:
sequence[2]
[[1]]
[1] 168.848 188.440 87.291 111.333 159.921 76.987 65.633 293.320
440.708
start[2]
[[1]]
[1] 2 5 8
end[2]
[[1]]
[1] 4 7 9
If you post the results of str() on all of those we would not face the
barrier of (re-)creating them ourselves. I happen to find it a pain to
have poster expect that we will edit all of their console output to
get back to a reproducible state.
I want to calculate sums of numbers in all start:end positions and
list the
output again, e.g. I can calculate the sum of the numbers occurring
positions 2 till 4 of "sequence", i.e. between start[[2]][1] and
end[[2]][1]
using this code:
sum(unlist(sequence[[2]])[unlist(Sfoot[[2]])[1]:unlist(end[[2]])[1]])
This code works perfectly fine but stops doing so if I put it into a
loop:
sums <- list()
for(i in 1:length(start)) { for(j in 1:length(unlist(start[[i]]))) {
sums[[i]][j] <-
list(sum(unlist(sequence[[i]])[unlist(start[[i]])[j]:unlist(end[[i]])
[j]]))
}}
The output looks like this:
durF[[2]]
Are we supposed to have intuited that "sums" was the same as "durF"?
[[1]]
[1] 387.064
[[2]]
[1] 302.541
[[3]]
[1] 734.028
instead of:
durF[[2]]
[[1]]
[1] 387.064 302.541 734.028
Something seems to be wrong with the indexing but no idea how to fix
it.
Probably your use of "[" rather than "[[". (Untested hunch.)
I
am not ambitious about creating elegant loops,
You aren't too ambitious about reading the Posting Guide. either.
they simply should work - so
please do not hesitate to make any suggestion: clunky or not, it
will be
greatly appreciated as I have been stuck with this loop for a week
now!
Many thanks, Tamara
--
David Winsemius, MD
West Hartford, CT
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