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.

Topic		Replies	Views
Summation Formula or Package in Julia General Usage package	0	261	November 26, 2022
How to perform this summation in Julia General Usage question	2	331	May 27, 2022
Think Julia Exercise 10.1 General Usage	36	2064	November 14, 2020
Accumulation in the for loop General Usage question	17	2315	January 21, 2022
Product and sum operator New to Julia	1	1477	January 17, 2019

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

Related topics