I was wondering if anyone knows of a library that easily handles expressions like this: [example] This would greatly help in what I am trying to do… This expression can be calculated using loops but in what I am writing end-users would have to calculate a lot of expressions like this one and I w…

I’m not sure what exact syntax you’re looking for but it’s easy enough to just do julia> a = randn(3,3) julia> sum((a[i,j] for i=1:2 for j=i+1))

Yes but this expression could be pretty much anything… The general form that I am looking for is this: [example2]

But you do have to specify A in some way. Are you not satisfied with things like for i=1:2 for j=i+1?

There is the problem that this A is not composed of numbers. So, for instance, in the first example, what I am really doing is saying for i=1:length(I) for j=1:length(J), if I,J are two sets and then if j=i+1 . But I have to do calculations where I would need something like: for s="new-york":"topeka…

Ok, I = ["i1","i2","i3","i4"] J = ["j1","j2","j3","j4"] T = ["t1","t2","t3","t4"] iter = ["1","2","3","4"] A = zeros((length(I),length(J))) B = zeros((length(I),length(J))) C = zeros((length(I),length(J))) for i=1:length(I) for j=1:length(J) A[i,j] = i+j B[i,j] = i*j C…

It is not clear to me how you expect to have something simpler than this. If you really want to avoid loops, you can do Z(i,t) = i == 1 ? NaN : sum(...) Zarr = [Z(i,t) for i=1:n for t=1:n]) # or Z.(1:n, (1:n)')

Yes, I guess you are right. I don’t really want to avoid loops altogether, I was just thinking that there might be a library that uses friendly syntax for this kind of thing. Anyway, thank you for answering, and generator expressions in sums helps quite a lot.

You may be interested in Tortilla.jl, it’s a work-in-progress by Peter Ahrens, see his talk at JuliaCon 2018. Also, there is Einsum.jl, TensorOperations.jl, and some other packages, but I didn’t personally use.

Anyone knows where I can get Tortilla.jl? I could not find it on Github.

Library for (algebraically) complicated sums (and other expressions)?

General Usage

Tamas_Papp November 21, 2018, 12:51pm 6

Please make an MWE. Gradually revealing specifications for a question makes it difficult to help you.

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Library for (algebraically) complicated sums (and other expressions)?

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