When I try to update a sub array of a vector with the lagged one, the result is a bit strange, is it the expected behavior?
MWE:
using ShiftedArrays
x = [1,2,3,4,missing];
y = lag(view(x, 2:3));
x[2:3] = y;
x
5-element Vector{Union{Missing, Int64}}:
1
missing
missing
4
missing
x[2:3] are both missing.
this is because y is lag of a view, so when you update the x[2:3], first it sets x[2] to missing, because that's the first element of y, but that makes the second element of y missing as well. (originally, the second element of y is 2). So by the time it sets x[3], it's missing too.
you need to make a copy somewhere, or update the array in reverse order.
btw, your code isn't doing much, if you simply want to lag by 1 and insert a missing somewhere, you can simply insert it:
julia> x[2:3] .= missing, x[2]
julia> x
5-element Vector{Union{Missing, Int64}}:
1
missing
2
4
missing