arraysfloating-pointintegerjulia

Convert float 2-D array to integer 2-D array in Julia


I know that it is possible to convert a Float64 into an Int64 using the convert function. Unfortunately, it doesn't work when applying convert to a 2-D array.

julia> convert(Int64, 2.0)
2

julia> A = [1.0 2.0; 3.0 4.0]
2x2 Array{Float64,2}:
 1.0  2.0
 3.0  4.0

julia> convert(Int64, A)
ERROR: `convert` has no method matching convert(::Type{Int64}, ::Array{Float64,2
})
 in convert at base.jl:13

How do I convert a 2-D array of floats into a 2-D array of ints?

What I tried

I could do it using the following code, which is a little verbose but it works. I am hoping there is an easier way to do it though.

julia> A = [1.0 2.0; 3.0 4.0]
2x2 Array{Float64,2}:
 1.0  2.0
 3.0  4.0

julia> B = Array(Int64, 2, 2)
2x2 Array{Int64,2}:
 4596199964293150115  4592706631984861405
 4604419156384151675                    0

julia> for i = 1:2
           for j = 1:2
               B[i,j] = convert(Int64,A[i,j])
           end
       end

julia> B
2x2 Array{Int64,2}:
 1  2
 3  4

An answer that doesn't work for me

julia> A = [1.2 3.4; 5.6 7.8]
2x2 Array{Float64,2}:
 1.2  3.4
 5.6  7.8

julia> round(Int64, A)
ERROR: `round` has no method matching round(::Type{Int64}, ::Array{Float64,2})

Solution

  • This answer is for Julia v0.3. For newer versions, see answer of DSM

    Use the int function:

    julia> a = rand(2,2)
    2x2 Array{Float64,2}:
    0.145651  0.362497
    0.879268  0.753001
    
    julia> int(a)
    2x2 Array{Int64,2}:
    0  0
    1  1