| letter {Biostrings} | R Documentation |
Extract a substring from a string by picking up individual letters by their position.
letter(x, i)
x |
A character vector, a BString (or derived) object or a BStringViews object. |
i |
An NA-free numeric vector. |
Unlike with the substr or substring functions,
i must contain valid positions.
A character vector of length 1 when x is
a BString (or derived) object.
A character vector of the same length as x when x
is a character vector or a BStringViews object.
Note that, because i must contain valid positions,
all non-NA elements in the result are guaranted to have exactly
length(i) characters.
subBString,
BString-class,
BStringViews-class
x <- c("abcd", "ABC")
i <- c(3, 1, 1, 2, 1)
## With a character vector
letter(x[1], 3:1)
letter(x, 3)
letter(x, i)
#letter(x, 4) # Error!
## With a BString object
letter(BString(x[1]), i) # character vector
BString(x[1])[i] # BString object
## With a BStringViews object
x2 <- BStringViews(x, "BString")
letter(x2, i)