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pythonbooleanlogicjulia
Joshuah Heath
Joshuah Heath

Reputation: 673

Logical operations on arrays in Julia

I have two nxm matrices of 1's and 0's (call them A and B). I want to convert them to Boolean variables and then apply "and" and "or" operations to them. In python, this is easy:

A = np.array(A, dtype=bool)
B = np.array(B, dtype=bool)
    
A | B 
A & B

However, I want to do the same thing in Julia, and I am having some issues. I first convert to Boolean via

A = convert(Array{Bool}, A)
B = convert(Array{Bool},B)

But then I do A&&B, I get

TypeError: non-boolean (Array{Bool,2}) used in boolean context

What am I doing wrong?

Upvotes: 2

Views: 1293

Answers (1)

Bogumił Kamiński
Bogumił Kamiński

Reputation: 69839

We first create matrices that store 0-1 values:

julia> using Random

julia> Random.seed!(1234);

julia> A = rand([0, 1], 3, 4)
3×4 Array{Int64,2}:
 0  0  1  1
 0  1  1  0
 1  0  1  0

julia> B = rand([0, 1], 3, 4)
3×4 Array{Int64,2}:
 1  1  1  0
 0  1  1  1
 0  1  1  1

Then broadcast using . the Bool constructor to get boolean matrices:

julia> A_bool = Bool.(A)
3×4 BitArray{2}:
 0  0  1  1
 0  1  1  0
 1  0  1  0

julia> B_bool = Bool.(B)
3×4 BitArray{2}:
 1  1  1  0
 0  1  1  1
 0  1  1  1

Similarly use the . broadcasting on & and | operators to get what you want:

julia> A_bool .| B_bool
3×4 BitArray{2}:
 1  1  1  1
 0  1  1  1
 1  1  1  1

julia> A_bool .& B_bool
3×4 BitArray{2}:
 0  0  1  0
 0  1  1  0
 0  0  1  0

Note that in this particular case using | and & on the original matrices would get an equivalent result (but the matrices would contain 0-1 integers):

julia> A .| B
3×4 Array{Int64,2}:
 1  1  1  1
 0  1  1  1
 1  1  1  1

julia> A .& B
3×4 Array{Int64,2}:
 0  0  1  0
 0  1  1  0
 0  0  1  0

Upvotes: 6

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