backward: Internal function for moving through secondary structures
Description
Given a bracket notation for RNA secondary structure and an index of a ")" bracket type the backward function will find the "(" bracket that closes the ")" at the given index.
Usage
backward(stc, i)
Value
returns the index of the bracket that closes the bracket at the given index
Arguments
stc
Array of brackets and dots.
a=unlist(strsplit("(((...)))...((..))",""))