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I try to compute the inverse fourier transform of a array of coefficients using ifft with Julia.

I have N complex numbers on an array organized as : Y=[Y_0,.., Y_(N-1)] representing my Fourier coefficients and by computing 

ifft(Y)

I get the following error message : 

MethodError: no method matching plan_bfft(::Array{Complex,1},
::UnitRange{Int64}) Closest candidates are:  
plan_bfft{T<:Union{Complex{Float32},Complex{Float64}},N}(::Union{Base.ReshapedArray{T<:Union{Complex{Float32},Complex{Float64}},N,A<:DenseArray,MI<:Tuple{Vararg{Base.MultiplicativeInverses.SignedMultiplicativeInverse{Int64},N}}},DenseArray{T<:Union{Complex{Float32},Complex{Float64}},N},SubArray{T<:Union{Complex{Float32},Complex{Float64}},N,A<:Union{Base.ReshapedArray{T,N,A<:DenseArray,MI<:Tuple{Vararg{Base.MultiplicativeInverses.SignedMultiplicativeInverse{Int64},N}}},DenseArray},I<:Tuple{Vararg{Union{Base.AbstractCartesianIndex,Colon,Int64,Range{Int64}},N}},L}},
::Any; flags, timelimit) at fft/FFTW.jl:601  
plan_bfft{T<:Real}(::AbstractArray{T<:Real,N}, ::Any; kws...) at
dft.jl:205  
plan_bfft{T<:Union{Integer,Rational{T<:Integer}}}(::AbstractArray{Complex{T<:Union{Integer,Rational}},N},
::Any; kws...) at dft.jl:207   ...

in #plan_ifft#15(::Array{Any,1}, ::Function, ::Array{Complex,1},
::UnitRange{Int64}) at ./dft.jl:268  in #plan_ifft#3(::Array{Any,1},
::Function, ::Array{Complex,1}) at ./dft.jl:58  in
ifft(::Array{Complex,1}) at ./dft.jl:56

Could anyone help with this?

when I ask typeof(Y) the answer is Array{Complex,1}.

Thank you

Cris Luengo
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ChrlTsr
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1 Answers1

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Just a guess here: ifft expects the array elements to be of type Complex{Float64}, not Complex. Furthermore,

julia> Complex<:Complex{Float64}
false

How did you get an array of Complex?

When using Complex{Float64} things work correctly:

julia> Y=complex([1.,2.,3.],[4.,3.,2.])
3-element Array{Complex{Float64},1}:
 1.0+4.0im
 2.0+3.0im
 3.0+2.0im

julia> ifft(Y)
3-element Array{Complex{Float64},1}:
       2.0+3.0im     
 -0.788675+0.211325im
 -0.211325+0.788675im
MBaz
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  • I initialize the array with the line 'Array(Complex,n)'. By using 'Array(Complex{Float64},n)' it works fine thank you. Although the answer is complex while I would except a real value function, I now have to solve a new problem. Thank you! – ChrlTsr May 25 '17 at 09:16