Finding Subsequences
Find subsequences of (integer) sequences.
occurs(subseq, series)
subseq |
vector of integers. |
series |
vector of integers. |
If m and n are the lengths of s and S resp.,
occurs(s, S) determines all positions i such that
s == S[i, ..., i+m-1].
The code is vectorized and relatively fast. It is intended to complement this with an implementation of Rabin-Karp, and possibly Knuth-Morris-Pratt and Boyer-Moore algorithms.
Returns a vector of indices.
## Examples patrn <- c(1,2,3,4) exmpl <- c(3,3,4,2,3,1,2,3,4,8,8,23,1,2,3,4,4,34,4,3,2,1,1,2,3,4) occurs(patrn, exmpl) ## [1] 6 13 23 ## Not run: set.seed(2437) p = sample(1:20, 1000000, replace=TRUE) system.time(i <- occurs(c(1,2,3,4,5), p)) #=> [1] 799536 ## user system elapsed ## 0.017 0.000 0.017 [sec] ## End(Not run)
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