when I want to extract a real part of g(x) and integrate a new function g1(x), the result b contains a Vector {Float 64} rather than just a number. How to get its integrated result?
Here is the code
g(x) = (exp.(-x).^2).*exp.(1im*x)
R_initial=real(g(x));
g1(x)= R_initial
b = quadgk(g1,0.6,0.7)
c = b[1]
Just do the following:
julia> g(x) = real((exp(-x)^2)*exp(1im*x))
g (generic function with 1 method)
julia> quadgk(g,0.6,0.7)
(0.021750435727577098, 3.469446951953614e-18)
In your code:
R_initial=real(g(x))
takes some global value of x that you probably have and R_initial is bound to some value. So you get something like:
julia> R_initial = [1.0, 2.0]
2-element Vector{Float64}:
1.0
2.0
julia> g1(x) = R_initial
g1 (generic function with 1 method)
julia> quadgk(g1,0.6,0.7)
([0.09999999999999998, 0.19999999999999996], 0.0)
which produces a vector in the first element as the input is multi-dimensional. Note that g1 is just a constant function.