Distance matrix

General Usage
1

I’m given a 20*122 matrix p. Each row of matrix is a 20-element vector. I want to calculate the distance between each vector and form a distance matrix. Here’s my code

   mul = []
for i in 1:size(p,1)
    push!(mul,norm(p[1,:]-p[i,:]))
end
mul = transpose(tiedrank(mul))
for i in 2:size(p,1)
    for j in 1:size(p,1)
    mul2 = []
    push!(mul2,norm(p[i,:]-p[j,:]))
    end
    mul = vcat(mul,tiedrank(mul2)')
end
mul

I got the error that

UndefVarError: mul2 not defined

How to fix this code?

2

in this matrix each row has 122 elements, because

julia> rand(2,3)
2×3 Matrix{Float64}:
 0.589931  0.0452219  0.840308
 0.469587  0.824793   0.702456

also, is this some sort of homework problem? if so please indicate that in your post

4

Sorry for my typo, each row has 20 elements. This is not my hw though.

5

Inside the j loop you create a local variable mul2, which isn’t accessible outside the loop. And even if it was, you reset it in every iteration. I would move the mul2 = [] up one line as a first step.

6

I tried it as

   mul = []
for i in 1:size(p,1)
    push!(mul,norm(p[1,:]-p[i,:]))
end
mul = transpose(tiedrank(mul))
for i in 2:size(p,1)
    for j in 1:size(p,1)
    mul2 = []
    push!(mul2,norm(p[i,:]-p[j,:]))
    end
    mul = vcat(mul,tiedrank(mul2)')
end
mul

But the value of elements in matrix are incorrect.

7

Here is a more explicit hint of what @gustaphe is saying:

function test()
  broader_scope = Int64[] # you should type your containers, as an aside
  for j in 1:10
    narrower_scope = Int64[]
    push!(broader_scope, j)
    push!(narrower_scope, j)
  end
  # One of the two objects between broader_scope and narrower_scope can be used
  # here outside of the loop. Try uncommenting each of these lines and calling 
  # the test() function.
  # @show broader_scope
  # @show narrower_scope
end