There's an open issue about it here:
https://github.com/JuliaLang/julia/issues/1845
I've also played around with a simple version based on a Set:
function uniqueind(C)
out = Int[]
seen = Set{eltype(C)}()
for i = 1:length(C)
@inbounds x = C[i]
if !in(x, seen)
push!(seen, x)
push!(out, i)
end
end
out
end
On Mon, Aug 11, 2014 at 1:22 PM, Peter Simon <[email protected]> wrote:
> Greetings.
>
> I didn't find any built-in function to return the indices for the unique
> rows in a matrix, so I tried rolling my own. I looked at, but didn't
> understand, the highly macro-ized, arbitrary dimensional code in the
> built-in unique() function. I did discover hashing, though, from looking
> at that code. Here is what I have so far:
>
> function uniquerowindices2{T}(a::Matrix{T})
> rowhash = Uint64[hash(a[k,:]) for k = 1:size(a,1)]
> hu = unique(rowhash)
> ind = zeros(Int,length(hu))
> k1 = 1
> for m = 1:length(ind)
> for k = k1:length(rowhash)
> if rowhash[k] == hu[m]
> ind[m] = k
> k1 = k
> break
> end
> end
> end
> return ind
> end
>
> This is quite a bit faster than my first effort, where I was comparing
> rows, rather than row hashes, but I'm betting someone out there has a much
> better way. Thanks in advance,
>
> --Peter
>
