Julia

Question

我想获取以下数组的绝对值：

x = [1.1 -22.3 3.01, -1]

即：我想要一个类型的输出：x2 = [1.1 22.3 3.01 1] 但是当我输入：

abs(x)

我收到一个错误：

ERROR: MethodError: no method matching abs(::Array{Float64,2})
Closest candidates are:
  abs(::Pkg.Resolve.MaxSum.FieldValues.FieldValue) at /Users/vagrant/worker/juliapro-release-osx1011-0_6/build/tmp_julia/Julia-1.0.app/Contents/Resources/julia/share/julia/stdlib/v1.0/Pkg/src/resolve/FieldValues.jl:67
  abs(::Pkg.Resolve.VersionWeights.VersionWeight) at /Users/vagrant/worker/juliapro-release-osx1011-0_6/build/tmp_julia/Julia-1.0.app/Contents/Resources/julia/share/julia/stdlib/v1.0/Pkg/src/resolve/VersionWeights.jl:40
  abs(::Missing) at missing.jl:79
  ...
Stacktrace:
 [1] top-level scope at none:0

Answer 1

Julia 不会自动将标量函数（如 abs）应用于数组元素。相反，您应该告诉 Julia 这就是您想要的，并在您的数组上广播标量函数 abs，请参阅 https://docs.julialang.org/en/v1/manual/arrays/#Broadcasting-1。这可以作为

julia> x = [1.1, -22.3, 3.01, -1];

julia> broadcast(abs, x)
4-element Array{Float64,1}:
  1.1 
 22.3 
  3.01
  1.0

或者你可以使用"dot-notation"，这样更合乎逻辑：

julia> abs.(x)
4-element Array{Float64,1}:
  1.1 
 22.3 
  3.01
  1.0

Julia - 数组的绝对值

Julia - absolute value of an array

math

linear-algebra

absolute-value