I have an array Xvals, of type Array{Array{Float64,1},1} which corresponds to a time series for a system in dimension d. I’d like to quickly look at the different components, from a longitudinal point of view; in other wrods, I want to plot (n, x_i(n)) for n=1,\ldots, and i\in\{1,2,\ldots,d\}. A “…

You are right, they are essentially the same, but still Vector{Vector{T}} has an advantage when speaking about allocations, plus a cleaner syntax (mm[:,i] vs. vv[i]). A more precise example: using BenchmarkTools function test_mat(mm) s0 = 0.0 @inbounds for i = 1:5000 @views s0 += sum(mm[:,i]) …

Yes, that is the allocation of the view object. On 0.7 it should go away.

I should add that part of the reason I coded this in terms of Vector{Vector{T}} was so that I could use the . operation on functions which would take in Vector{T} valued input. For instance, in my original example, if I want the time series of the norms at each time slice, I can use norm.(Xvals). …

Many physics based problems are unsuitable for Matrix organization of data. Consider: logging sensor data at different time intervals (e.g, temperature every 10 minutes, pressure every minute) regular vs irregular time intervals (e.g, temperature at regular interval, lab analysis results at irregu…

[image] gideonsimpson: For instance, in my original example, if I want the time series of the norms at each time slice, I can use norm.(Xvals) Yes, if this isn’t some dedicated algorithm and the rows (or columns) of matrix represent objects in their own right, what I’d do is a Vector of Julia…

There are also some cases where Vector{Vector{T}} becomes the natural choice. For example, I was once trying to find and store all non-zero elements in each row of a big random binary matrix. The number of non-zero elements is different from one row to another. With Vector{Vector{T}}, we can build i…

Simply to prevent data loss, you should be storing the data first in some sort of database. (That’s the sort of thing I used to work on - see https://www.intersystems.com/news-events/news/news-item/european-space-agency-uses-intersystems-cache-database-system-for-gaia-mission-to-map-1-billion-stars…

As another data point, LightGraphs uses Vector{Vector{T}} to store vertex adjacency information. (We keep the inner vectors sorted to improve lookup performance, bearing the cost at insertion time.)

There is a lot of overhead with Julia the Vector type. If the rows are not being modified (in length at least) once added to the vector of vectors, and rows are just added at the end, it might be good to use two vectors, one of the values, and another of the offsets into that vector. That will li…

[image] BLI: What is an efficient way to store and retrieve such data? (Array? Dictionary? DataFrame? Database?.. depending on amount of data, etc?) Your question is too general to be answered concretely. There are various trade-offs, which depend on the data size and structure. The most gen…

Quick Longitudinal Access to arrays

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Quick Longitudinal Access to arrays

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