Description Usage Arguments Value Author(s) Examples
Generate sequences, but unlike "seq", return NULL, when "seq" would generate a backward sequence. This function is useful for for
-loops, when empty loops are required in the case where by
is in the "wrong" direction, see examples.
1 |
from |
starting value of sequence. |
to |
(maximal) end value of the sequence. |
by |
increment of the sequence. |
NULL
, if (to-from)*by <0, otherwise
usual result of seq
i.e. seq.default.
Christian W. Hoffmann <christian@echoffmann.ch>
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 | seqm(12,4,-1) # 12 11 10 9 8 7 6 5 4
seqm(12,4,2) # NULL
lo <- 1; up <- 3
for (ii in lo:up) {
cat(ii," ")
for (kk in seqm(lo,ii-1)) {
cat(" ",kk) # do-in-lower-triangle
}
cat(" diag") # do-something-on-the-diagonal
for (kk in seqm(ii+1,up)) {
cat(" :",kk) # do-in-upper-traingle
}
cat("\n")
}
# 1 diag : 2 : 3
# 2 1 diag : 3
# 3 1 2 diag
|
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