[R] why the "[^\\d]" is not equal to "[^0-9]" in R regular expression?

[luofeiyu]

gregexpr(pattern="[^0-9]","+12345ty")
[[1]]
[1] 1 7 8
attr(,"match.length")
[1] 1 1 1
attr(,"useBytes")
[1] TRUE
gregexpr(pattern="[^\\d]","+12345ty")
[[1]]
[1] 1 2 3 4 5 6 7 8
attr(,"match.length")
[1] 1 1 1 1 1 1 1 1
attr(,"useBytes")
[1] TRUE

why the pattern `[^\\d]` has no same effect as of `[^0-9]` ?