How to convert a matrix from int to bool in Julia like MATLAB's logical()?

Question

If you have an array a of ints in MATLAB you can do logical(a) to get a Boolean array where every nonzero entry is 1 and every 0 entry is 0. How do you do this in Julia?

Answer 1

Another option is to use the iszero function, which gives you a clearer syntax:

julia> a = rand(0:3,2,2)

2×2 Array{Int64,2}:
 0  3
 0  1


julia> b = iszero.(a)
2×2 BitArray{2}:
 1  0
 1  0

You can find information about iszero in here or by typing ?iszero at the REPL.

The use of broadcasting is needed because that makes the function compare every element to zero. If you don't use it, it will return only true if all the matrix is zero or false if one element is different than zero.

Answer 2

You can construct this behavior by broadcasting the inequality operator.

julia> x
5×5 Array{Int64,2}:
                    0  -4107730642120626124   6654664427866713002   7518855061140735034   8818106399735122346
  8091546149111269981   4315717857697687985                     0  -5798218902015720994   1300970799075893685
 -7301322994135835673  -2297242472677021645  -4021288767260950802   7892625078388936975  -1629449791447953082
  1060255079487701867  -5212584518144622345   7329251290490888722   1375278257655605061  -4361465961064184585
  -469090114465458856   6912712453842322323  -1577327221996471827  -5606008086331742040   1641289265656709209

julia> !=(0).(x)
5×5 BitArray{2}:
 0  1  1  1  1
 1  1  0  1  1
 1  1  1  1  1
 1  1  1  1  1
 1  1  1  1  1

The result is a BitArray, the canonical representation of a matrix with boolean values.